Here's my problem.

For all I know, the old bolts were 9/16". The thing is, I didn't bring any of the old bolts with me so I can only assume that since all the other chainplate bolts were 1/2" that the backstay bolts were 1/2" also. This my not be the case and it's possible they really are 9/16". (just didn't think they might be different but it's possible and I don't remember )

Van posted that Jamestown has them in 9/16". In an effort to cover my ass, I'm ordering some 9/16 bolts. (Thanks Van, I couldn't find them locally and thought they were unavailable ).

There is no 'backing plate, only the 2" thick fiberglass knee and some giant/thick fender washers.

The other thing is that if the holes are really 1/2" I don't want to try to drill out the fiberglass to make it 9/16 and would rather leave them as they are. The fact is that I don't know being 3,000 mies away. Purchasing 1/2" & the 9/16" bolts are the only way to cover myself.

As far as working fine for the past 25 years, here's a couple of photos. I had the same cracks in 3 of the other ones. Funny thing is that none of the cracks were in the top holes. That means that even if it did break at the crack it wouldn't have parted.,,,,, Except for the one that broke on the passage from hell, It broke in the middle of the decking above the bolts.

Thanks again Van,,,,,, I should have tried Jamestown before giving up. I think with them I'll be covered.