The two screws adjusts the strength of the ball plungers that hold the quick release pin in place. They should not wear out easily, but if the pin is too loose, you can tighten those two screws.
The middle hole is for a bolt that can be used to more permanently hold the SQR pin in place as a backup option. Nobody has told us that is needed, but the hole is there anyway.
Thanks @Mika. My ball plungers screw are quite loose and having some minor “klonks” on fast reaction wheel turning and it is annoying me. Maybe be also wheelside screws causing.
And solution to “klonking” sound and loosenes was that those ball plungers screws were loose and loosenes and klonks disappears now. Finally. This problem was since I got my cube. If some one has similar problems,hope this helps.
Mine (first batch) are hard to plugin, really Hard.
Im plugin only by one side (right side), if it wears out any time, I can change by the other one or plugin the left side
Same here, putting the pin in requires some strength. The SQR is perfectly tight for me as well.
@Mika , question on that middle hole. I am planning to use Buchfink Q1R with SC2 by bolting it to extension piece (New Simucube wheel adapters), so can we just screw bolt through that hole and skip the locking pin.
What kind of bolt is needed, is it included in the package, if not can you please point to exact model on something like https://www.mcmaster.com/
Thanks a lot
I can’t remember the bolt specifications off hand. The locking pin must be used even with the the bolt, as the bolt is just used as a backup for the ball plungers.
Really? 
Somehow I thought reading earlier that sticking out pin can be replaced with the bolt to make it look cleaner.
It is meant as a backup for those crazy people that would use the SQR with stronger than specified forces. In nominal case, the torque is handled perfectly via the SQR design, but if there is a strong force in line with the axis of the ball plungers, and the driver uses both hands to apply a force to that direction, that force can be greater than the force of the ball plunger springs, causing the SQR wedge to move slightly. It is for this kind of use case the bolt is to be used for. But, not even the crazy tester from down under has reported to see this kind of phenomena.
I immediately thought of the crazy one from down under when you said crazy people :)
So the only way to get rid of the locking pin is to unbolt SC2 QR from hub and use Martin Ascher adapter?
New v2 wheel side QR mount does not have holes matching hub 3 bolt pattern by any chance?
Me too …haha…
But yes, under normal operation, I have not seen any issues with the QR system.
For those interested: I have also been testing HRS Xero-play QR. It comes with a suitable flange that allows removal of the wedge of the SC2 QR, allowing bolting the Xero-play directly to the hub on the SC2.
It makes for a much cleaner solution, if you wish to use a different QR, than bolting 2 different QR’s together. I think those of you that have a lot of Q1R units, you will need to speak to a Holger to make a suitable servo-side plate then.
But then again, it will be cleaner to just get additional wheel-side plates from GD for the SC2 and stay with the SC2 so,union, it is very clean, minimalist and functional. Plus super-easy to use.
SQR is a nice robust QR but a bit bulky on a wheel side and not really better than Buchfink Q1R esp for those who invested into that system already, I see why Barry Rowland and others still prefer it over SQR.
Too bad Ascher adapter is out of stock everywhere, if anybody knows where you can snatch one, please pm me.
Thanks
How much time did you actually drive the new SC2 QR?
I do not have my pro yet. Hopefully soon.
Not sure what route to go with QR yet.
Fortunately I still have some Q1R stuff for myself.
It looks like the total length of the SC2 QR is much longer than we had with SC1?
I did a pretty hefty stint testing it out, never had issues. Only reason I went with Xero-play was because I am swapping between different systems, like the Ult, Pro, Bogeyman, and Mige/Lenze setups, as I am constantly testing and evaluating ffb stuff.
But if I had adapters and servo-side GD QR for all wheels, no issue to use that.
My Holger QR1’s are lying in my drawer, under high-torque, I have some play on mine, and I have about 4 or 5. They all do the same. So they made way for the better (imho) HRS Xero-play. Plus, the HRS one just looks so much better.
Yeah some of the Holgers the material thickness was a little different so it required adjustment every time.
Bretto’s new ones look AWESOME, but I am pretty poor these days.
Can’t afford them
Love the Xero QR system, so easy to use and zero play.
Yeah, I know what you mean. I have succeeded in breaking a servo-side once. Tightened it to a good level, then mid-race, running a dw12 at 38nm torque on Bogeyman, the retainer mechanism bolt snapped, I almost tore myself a new arse.
It was scary when the clamp-bolt just let go, with all that torque applied, I was all over my rig. Gawd. Not fun.
Holger was great in providing service and spares, plus extras, very happy…but when Xero-play came along, I knew this was the one for me. No play at all after many months of abuse, I own 3 servo-sides and 5 wheel-sides, as tight as day 1.
Happy there is another sturdy QR out there 
Like said, if it wasn’t for the fact that I am testing different systems all the time, the SC2 QR will be more than good enough.
Wow Beano, that doesn’t sound like fun at all. Hope nothing was damaged or hurt.
If you rated QRs you used, which order would you put them?
Hi Andrew, ha, just a few bruises and dents, nothing that I couldn’t buff out 
But in all seriousness, had a pretty tender right-side rotator-cuff for a couple weeks, the shock-load was pretty bad. But I survived.
After that episode, I opted to run fixed mechanical connection, no QR, until the SC2 came along. That’s when I bought my first HRS Xero-play QR, which went onto Bogeyman. I have since fitted them to all my Servos.
I would rate my favourite the HRS Xero-play, then the SC2 SQR, then the Holger QR1…and nothing else close to these 3, tbh…but like said, if you only ever use the SC2 servo, the standard SQR fitted will serve you well. It’s a very good, effective and clean design.
If I did have access to a few extra servo-side SQR’s, I would have had no qualms running them on Bogeyman. Might actually retrofit one to test, as I can drive that servo to almost 40nm. But this would be exceeding the design-specs, but it will anyway be good info, I suspect it will survive without to much hassle…