Haven't done this in a long time but this is a great procedure. From the scraps of ABS cut long strips about 1/4" wide. Clamp these at either end of 1/2 the cowl. Now fit the other 1/2 cowl - this will take some delicate sanding. Put the two cowl pieces together and wick in some Laquer (dope) thinner into the seam. This will soften the ABS and actually weld the two cowl halves together along with the strip inside. It will be much more secure than fiber glass. As mentioned above, fiber glass doesn't stick well. Good luck.

Phil