Gee, I don't think I'd call that "fitting well". What was the source/brand of that undersized windshield?
I put a ProSource windshield + Classic Alfa seal in my Duetto a few years ago. It just went in, with no futzing around needed. My installer did use black sealant at the base of the gasket, where it fits over the clips - rainwater would certainly come in around the clips without sealant. I don't think he applied any sealant between the glass and gasket.
It was a ProSource product and I am quite happy with it even though I needed to jump through a couple extra hoops to make it work.
I think that is a "fits well" for reproduction parts. "Fits horribly" or "doesn't fit at all" is all too common with reproduction stuff. Actually, "isn't correct" is my usual complaint.