Here is a web site that has an FOC calculator:http: //www.goldtip.com/calculators/foc.asp
Hope that helps you determine yours.
It is for vertical bow carbon arrows but works for bolts too. (The formula works the same for aluminum shafts).
I have not used the system you mentioned, looks like to much 'putzing.'
I use 20" GT Lazer II (carbon) shafts, 110 gr brass inserts, 2" Blazer vanes (no wraps) and the stock GT rear alum. Tipped with a 100 gr Slick Trick I get a FOC slightly more than 20%.
The stuff I've read says around 12% for arrows and "higher, perhaps as much as 15% for bolts." This sounds like the author wasn't too sure about the latter , so I experimented. All I can tell you is that my bolts with 20% FOC (and Slicks) are very accurate and consistent.
I mention Slicks (smallish, 4 bladed heads) because I've found larger, 3 bladed broadheads I tried less accurate by lacking consistency from one bolt to the next.
BTW: I found brass inserts in 90 and 110 gr weights; there may be others.