albertr,
I am pretty sure my seal is original - matches other EVCs I have seen. The seal at the bottom in the photo looks like mine. The piece that grips the top has metal in it; does yours? Mine is also black, not grey. At this point, just install a piece of the original in the gap and try it out. If no leaks, then it works!
Who/where did you buy it? What did the vendor say about length?
Who does sell an original replacement? From the Winnebago parts diagram, it is Winnebago Part #131559-01-000 ("seal-bulb-poptop") , but I do not find it in the Winnebago catalog, even though they do have other bulb seals in the catalog. I looked up that part on Lichtsinn's site, but no luck.
Gowesty sells a replacement for about $110 and Eurocampers sells one for about $120. Eurocampers also says it is "high quality aftermarket, original seal discontinued" and that its seal is 27ft. long. The Eurocampers seal gets high reviews "This item works as indicated. It goes on easily by hand and without glue because it has internal metal threads that grip the fiberglass poptop. It has stayed on through multiple openings and closings this summer."
FYI - My seal, too, has a slight gap - maybe a 1/2" where they meet. But I did notice it is installed with that gap at the front of the poptop, not the rear. Maybe because at the front, it is protected by the cowling of the luggage rack?