I didn't have any control flutter on my Predators either, that was never a problem for me.

You should tighten up that covering, or apply an X of tape, that should help the wing twisting. The Predator really needs that skin stiffness. (at least the older ones, I haven't seen a brand-new one, mine we bought around Feb of last year).

The .32 on the front of the Predator is awsome. I was going to fly a C class RCCA combat event, so I pulled my Mag .25 and put in the OS .32F, with a mousse can and an APC 9x5 prop. The power difference is stunning. It was easily the fastest plane at the event. However, getting ready for that contest, I did, in fact, buckle the spar really badly, the plane looked like it was flapping it's wings, really quite funny. A .32 is just too much power for a stock older Predator. I wound up "fixing" the spar by expoxying in some carbon fiber doublers on both sides of the spar. It flew ok, but I didn't get it straight, so the wing had a bit of a warp in it, and it snapped more than it used to because of the warp.

Other than fixing damage, I haven't had to do any "maintenance", but I actually didn't stay with the Predator design that long, I think I only flew them the first part of last year.

When I built mine, I was trying to keep the CG as far forward as possible so I wouldn' thave to mount the engine way out on the beams. So I put the servos, battery, and RX pretty close to the spar, and the servos were sideways. As a result, I think there wasn't enough foam on either side of the spar to stop the buckling under the loads the .32 caused.