Here is the first of 3 for me too I have always flown it with an OS61FX and guess I never had any problems with the covering as all 3 are/were stock. I still have the 3rd one and fly it once in a while. I liked the design so much that I bought the US lite and put on a G-26 for a power plant. (see pics)

The history of my US 60's is: First one was a dumb thumb move. I was doing aileron rolls and came out inverted. My thumbs did the right thing and started to push forward to gain altitude, but my brain got in the way and I pulled back only to drill it right into the ground. I decided I wanted a second one and went to the LHS where they had one already assembled and only $10.00 more than the ARF. Since it had upgraded hardware, I bought it and also used the OS61 for power. I would probably still have it, but in a split "s" I was about 3/4 of the way through and the right wing completely separated from the rest of the plane. I was only at about 1/2 throttle, so I knew I hadn't put too much strain on the design. Well after a close inspection, it was discovered that on the right side of the wing joiner, very little epoxy had gotten between the joiner and the wing support spar. So when the extra stress hit the wing, the joiner and spar separated right along the joint. On my third, I made sure this part will not separate.