JOE!! Why don't you just dowel the old holes from the front? thin ca them in, then drill your new bolt pattern. the old nuts can be worked loose if you really try. Wouldn't you want your DOCTOR to explore all the options before he knifed into you[X(]? Even if you had to cut a hole, try the patch with the lowest heat that it takes to get the edges of the patch to stick, that's what tacking means. Once you have a seal all around, then increase the heat untill your patch shrinks. If it isn't up to your standards, cut the patch out and keep trying till you get it right. You said you got a whole roll? If it won't stick, then it isn't clean enough.