You may find it to be a little sensitive with the CG that far back. Do not add any tail weight! Take the airplane out and fly it. You should have no trouble flying the entire stunt pattern with it balanced there. The general rule of thumb for older airplanes like the Fightstreak, even the Sig Twister and Banshee, is that they will fly fine with the CG 15% of the mean average chord behind the leading edge.

Incidentally, I just started a Brodak kit. There are starting to be Flitestreak stunt events around my area. I don't care to have an ARF, but several of my friends have them and they fly very well.

Jim