Your problem is not the size of the engine !!!!! What happened is that when you dove and then pulled back, the force stretched the rubber bands, letting the wing rise above the wing saddle, and thats when the wing root gave way. With a 46 FX, you should have had at least 14 to 16 bands in place for that dive/climb. Go even 1 step further and modify the plane for wing bolts.
In our group, we have determined the AVISTAR to be the best funflyer/trainer/windflyer on the planet. The FX 46 is a nice upgrade for it. Don't use old rubber bands eighter, and keep them in a baggie with a little talcom powder to absorb the fuel/oil which breaks them down sooner. Dennis (Red Bluff)