Former member Bob Scoggins was the one who eliminated the tank panel. You can
see a pic of the bike at Friar Jonh's website. I don't think Bob joined the new site since he sold the bike. It's not as easy as just filling in the area under the tank panel. The fuel filler bung is raised up quite a bit to fit the top of the tank panel. IMO it wouldn't look right if you just bodyworked the recessed are and didn't do anything about the raised gas cap. If you look at the pic in the link above, you can see that Bob welded in a new bung that's in a different spot than where the stock placement is.
If you have experience at this sort of thing it's time consuming, but doable. If you're a rank greenhorn like me who's never welded, this can be a daunting task. A local custom builder could be an option if that's the case.