Yammahoper,
You are right as the old Arms Comp is very optional for RMSS/FRP as it is for RM2/C.
IMO you should ask your GM first. Second would be to show him the stuff in the book and state your case. Third we can help you stait your case but we should know what rules you are using as they can make a big difference. Also I have heard of many house rules in use for ExP's and actions, load, movement, lack of sleep, spell effects, etc.
From what I remember ExP is 1/2 pt per round for light and med wepons and 1pt for heavy weapons. You exert more points for actions such as running and carrying heavy loads.
I can also tell you ExP's are one of the rules frequently ignored by GM's playing RMSS/FRP as it is a lot of bookkeeping unless you are using a computerized combat tracker to aid in all the number crunching.
MDC