That is what I thought, 5/16 factory and 3/8 for after market glass. I had 2 windshields replaced by my local glass man, one in a 68 and the other in a 70 GS, he said he used 3/8, not sure if it was 3m, and with the old clips all the trim fit. Loren and I tried to set the rear window in my 66 with 3/8 and the trim would not install. We have the correct clips, but new, and had to remove the butyl and start over. I bought a 1/4 and5/16 3M kits and have not tried to install it the second time. I was told the 3M does not compress much. Wonder if there is any tricks to get it compressed? Like setting in the sun, or heat the butyl or use a roller on the butyl before you remove the paper? I think I am over thinking this. Also 66/7 hardtop rear window trim can be problem to install and the new clips may add to the problem.
