Rusty, you might consider clecoing a temporary .025 aluminum extension flush with the outside and extending it aft. Wax it before installing it. Scarf the aft edge of current cowling so that the outside TE stays but remove some material forward and inward. Now lay glass up to current cowl thickness. Grind off the excess layup on the inside forward to make a smooth inside surface. Now lay glass aft edge to several inches forward. Maybe some of the composite airframers have a better idea, but believe this would work.

Thanks for the comments.  I've done something similar to that in the past, and was thinking about maybe using posterboard and duct tape this time, instead of aluminum and clecoes. The biggest challenge is to clean the cowl well enough to get the oil off, and get something to stick to it.  I've got the cowl and all my epoxy crap at home, and will work on this during the week.