Em, RC, actually I do use epoxy as a filler. Here's how. I mix up a batch of finishing resin (2 part epoxy) and then triple (or more) its volume with micro-balloons. Makes for a very stable and sandable filler. I used it to: fill the nooks where the stab butts against the fuse; ensure that the wing saddle mirrors the bottom of the wing (the right saddle needed a 1/32" shim to square the wing with the fuse); and fill around the rudder control rod tube where it exists the top of the fuse. Just enough to fill the gaps to help out the covering around stab & rudder controls.

Here's the laundry list:
<ul>[*].4 oz - 12 oz tank (replacing 8 oz tank)[*].7 oz - replace 3" engine mount with 3.5" SIG mount[*]6.0 oz - replace OS46LA w/ Evo 52 NX (center of mass 1/2" farther away from firewall) [*]2.5 oz - replace spinner w/ Higley heavy hub[*].9 oz - replace wood prop w/ APC prop[*].5 oz - replace 1500 mAh NiMH 4.8 w/ 1100 mAh NiCd 4.8 (or 1400 mAh NiMH 6.0 or 2300 mAh NiMH 4.8)[/list]Total is 11 oz - most in front of the firewall. If the engine center of mass is far enough forward (additional 9.4 oz) might bring it close. Good news, all of this stuff is "on the bench" - biggest pain will be relocating the blind nuts for the new engine mount.<br type="_moz"/>