RE: Can anybody help with my F.O.C issues
 

You've got it backwards, it seems. Going to .500" deflection is going to a weaker spine than 340's and would be underspined for a bow that needs a shaft that deflects.340".

An arrow that is so stiff it cannot be deflected by the spine tester would have a deflection of zero. On the other hand, an arrow that deflects a full inch in the spine tester would be very weak.

The lower the deflection number, the stiffer the spine. The hgher the deflection, the weaker the spine.

RE: Can anybody help with my F.O.C issues
 

With your specs you can shoot 125 grain heads and feathers , no problem , should up your foc considerably , a guess is 13-14 % , forget the 500s , they are way too weak

RE: Can anybody help with my F.O.C issues
 

I shoot a similar setup, 63lbs, 28" draw I ran my specs through thearcheryhut calculator here's the result:

cx300 28.75 inches, 8.1 grains / inch 232.875
nock 8.7 grains
insert 11 grains
3 blazers 15grains
Montec 100 grain

arrow weight 367.6
KE 64lbs
FOC 12.4%
280.fps

3 pass throughs at 14,16, and 32 yards

RE: Can anybody help with my F.O.C issues
 

I just ran your numbers and came up with a FOC of 10.9% with the spine being marginally stiff.

If you go with a 125gr head the FOC will be around 13% and a slightly stiffspine which is better than a slightly weak spine.

I would not advise on cutting the shaft back as that will stiffen the spine too much.