[Greg McKaskle]

You may also want to think about where various elements are attached to the belly pan, especially the heavy battery. It looks like the battery is floating in the center of the pan's unsupported edge and your straps that pull your catapult are attached to the very edge of the U. When loaded, the frame will flex. When suddenly unloaded, the frame will move the wood in one direction, but the battery's inertia will resist. This will require the wood to accommodate the strain. The breakage will occur where the flexible wood is no longer allowed to flex -- where it is bolted to the frame.

If you move the battery to another location within the U, that would help a lot. You may also consider mounting the battery to the frame instead of the pan. The rest of the electronics don't have nearly the same mass, but the same principle applies. If you can reduce the flex by bracing the gap, that would help too.

Greg McKaskle