It's a little work and you need a grain scale, but, when I was shooting alluminums I took the inserts out. I then went to the hardware store and found some long screws that would fit in the bottom of the insert.
I screwed them into the bottom of the insert, just a few threads, and weighed them. I cut off the head of the screw and whatever else I needed to match find the desired weight.
I then epoxied the screw into the insert. Around the end of the screw, where it was cut, I wrapped electrical tape so it was snug against the walls of the shaft.
Re-insert your insert and you now have FOC. Hope that helps.
For heavier tips look at 3 Rivers web site. I believe they have quit a few selections.
-Jeremy