spring relocate and mini tub

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.