My shield measurements are from the upper edge of weatherstrip. Looks about like a 9 3/16 in the pic above using my method. Maybe 10 ish at the bottom of the gasket.

Dshark was one of the earliest owners, and we believe it might have been possible he rec'd a GL base instead of an F6B base.

Bruce B got his shortly after Dshark, and he had the shorter base. (Pics in this thread)

My bases so far have been somewhere around ~8~,, maybe a touch above 8,, from top of strip to top of shield.

If memory serves, that's about the same as Bruces 1st base,,,