^^^^^^^^^^^^^^^^^^^^^^^^^
Similar to what I might do, but would bring the inner panel out to be flush w/ the inner fender well to make it smooth and to look like one piece, carpeteed. -----(think I said that right) .I did find some pics on line of carpeted, no seats rear areas where the builders cut the lower sail panels to allow the tub tub extend into the space and carpeted the whole deal (attached). Personally I would probably either strip (carpet) the lower panel to metal, than split,stretch and fill (gaps)then recarpet. Or use a piece of cardstock as a form and make a fiberglass piece to fit.
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I'm sure it will look great. Pics though, please.
I was and still would still like to see it in progress. (if you don't mind sharing)408, if ur talking to me, I ain`t started it yet !!