Alright, update time:
Went out to the field Sunday to try flying it again. Unfortunately, no video this time (which would be useful to analyze the "flight" in slow-mo).
It was a short flight and everything happened pretty fast so I'll try to explain it the best I can.
First, I tried an unpowered glide test, but with the extra weight of motors, batteries, and electronics it really doesn't like slow speeds. It just lazily arcs down (probably too high of a wing loading).
Then I went for a low power launch to minimize the thrust line effect... It launched fine but the slow speeds make for tricky controls.
About 12-15 ft out it porpoised a bit and I tried giving it some power, as it started to climb it suddenly slid the tail to the right and then rolled hard left. At this point it was about 5 ft above the ground so it just "landed" on it's roof.
Damage report:
Slight damage to one of the winglets, easily repaired with some tape in the field.
Battery tray dislodged itself from it's mounting, not field repairable.
Diagnosis:
I have a felling it's a wing loading issue but I have limited experience with RC planes so...
I'm not eliminating the possibility that is was pilot error.
I'll fix it up again and try again.
I was thinking of replacing the elevons with longer ones to both extend the wing chord and increase control authority.
If that doesn't work... I'll probably need a better pilot to give it a try.