Odd question, but what is your definition of a big wrench?? IF its truly big enough you will twist the head off of said bolts. I know you don't want that to happen but at that point you can grind it flat, center punch it, and drill it out. You may not be generating enough breakaway torque. If you are using an end wrench it's not big enough. If you are using a socket and a breaker bar you are getting closer, but put a cheater on it.
If you are that determined to remove these bolts. Otherwise just be happy that pylon is tenting cover a bit. Without seeing your cover I can't make definitive statements, but really just pay for either a Hangtyte, or reinforcement and tent pole forward of pylon so cover shedd water properly and you won't care about the pylon.
Most properly tented covers will never touch the pylon
If you are that determined to remove these bolts. Otherwise just be happy that pylon is tenting cover a bit. Without seeing your cover I can't make definitive statements, but really just pay for either a Hangtyte, or reinforcement and tent pole forward of pylon so cover shedd water properly and you won't care about the pylon.
Most properly tented covers will never touch the pylon
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