The covering does "sink" in between the ribs, however this is not a mistake. The wings leading edge is not sheeted and that is why it does this. Not to worry though, it doesn't affect the flight.

I am using the Park 480, Eflite 40 amp ESC, with APC 11x7 E prop, TP2100 Pro-Lite. Berg Rx. I am going to maiden mine today, or perhaps tommorrow. I really like this plane and have it setup like the manual said. The only thing I am going to change is the landing gear. The gear is sturdy enough, but I don't care for the design of it. JMO.