Listen you got all good info here so far. I too have a open glock and after ALOT of load development I settled on 8.5 of hs6 with a mg 124 loaded at 1.166 I'm using a kkm barrel and a 11 port sjc comp and a 11 pound ismi flat recoil spring. I tried all the 4 port comps, sjc, jagger, carver etc and couldnt get the gun to shoot the way I liked. In my opinion in 9 major you need the 11 port to get the glock to shoot flat. However it does slap the hand pretty hard but that just means the recoil is being transfered back instead of up which is a good thing. The glock is a light gun compared to most other platforms so it takes a little more to get it to behave.
You may want to consider a different barrel, comp combo. Hope you don't give up on the glock. If you need any more help feel free to ask.
Joe