I bought the UNV adapter and their single screw Acog mount. The bar on opposite side from the thumb screw is spring loaded with a pretty stout spring. It has two cross bars to engage the rail slots better. The key thing about it being spring loaded is that its easy to remove and reattach one handed. Grasping the Apex across the top, you depress the thumb screw with your middle finger and kind of roll it onto the rail. Since is is fairly secure at this point, you can use the same hand to make sure its pressed firmly forward, then tighten the snot of out the thumb screw. This allows you to use the Apex as a monocle for scanning, then easily reattach the scope while you hold the rifle in the other hand.
My brain tried to tell me it just couldn't provide good return to normal, but I went through two boxes of ammo playing with it and I was impressed. Since thermal is a little more challenging on the target range (your hot or cold bull tends to grow and spread across the target) trying to talk group size is probably a little unfair...but return to zero was more than adequate to dispatch several juvenile raccoons at 165 yards.
NRA Lifer / Member TSRA