I used the plastic cowl on mine, and used silk and epoxy to reinforce the seam. Also be sure to reinforce the area where the mounting screws pass through . . . and make sure that part of the cowl rests flush with the fuse. I'd also reinforce the area around the muffler cutout just to be safe.
Overall, that seemed to work fine. The plane came in at 51 oz, heavier than I wanted, but flew great with a B-40. The plane was built with all kit wood, maybe a reason for the weight. I have a second on the building bench now, it will include some of the Dave Fitzgerald mods. Can't wait to fly that one.
Brian