I had the same problem - If I hit a bump on takeoff I could bend the struts I had so much they wouldn't retract properly. The original struts in the plane were fairly soft steel, and 5/32 diameter.

I replaced them with 3/16 Spring Air struts. The increase in stiffness was much greater than you would expect from the increase in diameter. I went from having to bend them back every time to never at all, even with some rather harsh landings.

I though that I would have problems with the wings or retract units, but they seem to have held up. The plane in question weights 13 lb dry. I mostly fly from tarmac, but I've been caught short a few times and had to land on grass runoff areas without any problems.