Assume you are going to shoot a 350 grain arrow. Assume you are going to shoot 70 pounds of draw weight. You have a 27.5" draw length. Assume that your bow will reach top speeds of 335 fps IBO, most seem to fall right in the middle of the speed ratings. Add in the loop, string silencers and a peep........ we will assume these are the lightest weight available IE: meta peep, shortest loop possible, only two leeches.

You loose aproximately 10 fps per inch of draw length lost so you are starting out at 310 fps right out of the gate, again assuming you have a fast bow to begin with. Add in the string stuff and you will loose another 10 - 12 fps. You will be real lucky if you hit 300 fps at 70 pounds draw weight.

I would still use the speed mods butI would not expect to get 300 from your specific set up unless you upped the draw weight or lost some arrow weight.