I was thinking of this thread today while I was tying something down in ky truck. I'm sure this is a very nice car, but I think you are better served by bolting a proper bracker than trying to use a sheetmetal hole from the factroy. I'm sure they only had intentions for it to be used one or two times. Here is a bed rail hole on my truck. I have over 250k on it and it is well used. I still would rather weld up two bolt holes than reproduce the rolled opening on a frame rail hole.
Another idea would be to disconnect the shocks, maybe?
