ORIGINAL: ameyam
Additional images attached.
You will note that there are no stringers anywhere. This is just interlocking ply construction.
See the video how the wood flexes with just a little pressure. As stock, this model was meant to fly of tarmac and can take no abuse.
Ameyam
I see nothing wrong nor that needs "fixing", nor anything "wrong" with the quality. It is a 3D plane.
Yes the model is best flown off tarmac, if you want to fly off grass just pull off the pants and add bigger wheels.
Lite ply bends when you exert sideways pressure on it. That's the way it is.
Again you're overthinking it.
As someone once told me, "improve the pilot not the plane" when it comes to adding strength for landings, etc...
This appears to be built to be a light and agile flyer.
A 20cc is right for this plane, a 120AX is likely to be VERY overpowered.
If it is tail heavy don't change the engine, instead put the battery packs on the nose, beam mounts, etc... move the rudder servo forward and move the engine as far forward on the mount as you can.
Check out this Youtube video of the plane flying with a 20cc DLE on it... it is MORE than enough... the guy is doing 3D stuff with this plane...
[link=http://www.youtube.com/watch?v=If0i6Xa8HGw]Click Me![/link]!