The minimum suggested OAL for 9mm is 1.000", so the number you quoted... while short... is not without merit. Berry Mfg 124gr flat points load at 1.065" and they shoot fine.
Some other thoughts...
? "The proof is in the pudding" as they say, so the thing to do is load up 40 or 50 and go shoot them. Generally, RN feed really well in a CZ. If there's no problem, then what have you got to worry about ?
? I picked the 0.015" number because with novice reloaders the OAL seems to vary quite a bit over 50 rounds. If you're experienced, got your process ironed out, and your OALs don't seem to wander, then you can cut that to 0.010" or even 0.008". The object is to simply get the slide to go all the way into battery and be able to shoot safely.
? But you're correct, a slender profile RN should easily be able to load at 1.125".
Hope this helps.