My Walthers won't eat MG 124 JHPs loaded any longer than 1.075", and I've put as much as 4.2 grains of VV N320 behind that bullet at that OAL in order to make ~130 PF out of a P99c (3.5" barrel). Primers were starting to get just a tiny bit flattened, but nothing scary. 1.09" OAL with a 124 gr bullet and 3.7 of a powder with a very similar burn rate wouldn't scare me. As always, be careful and use a chrono, but you're probably fine.