You need to go into guerilla and open up the globals.globals file in the globals folder. You will find 3 sections, multiplayer information, player information, and a section go change your FP arms model. Change the bipeds in mp section to one designed for mp (you will normally be able to tell if the biped has _mp in the filename) and change the one in player information to one designed for Single player. And for FP find the FP.gbxmodel you want to use. Hope this helps.