Whoever put the all of the 6 tops I had, now I think about it did things differently. Note 256/4 in the parts blow up, that's a completely different metal shape. The holes are also different on that metal corner piece holder possibly the later ones that may require trimming of the corner pads. As always change is always constant.
How does it go together? there's more than one way to skin a cat, right way, wrong way, you're way whatever.
The pads being to thick or too narrow likely lies in the mfg. and or the compound of rubber. As I said the CAT made corner pads were very thin when compared to S.S. ones.
My car still has the footprint of the top carried by the PO as it came from the S.F. Bay area. Never bothered to cut and buff them out as the tonneau did about the same thing then I'd have to respray the car. Got 4 seasons and a 4 season car and no car trailer, maybe you need a hard top, I don't yet.
I still maintain that watching is nothing like the hand strength required to coerce rubber into a painted channel. Or likewise do dam near anything without a lift as that would even make watching not as fun.
I'll snap a picture of 256/4
It's been probably 10 years since the first top was disassembled.