Hi guys - a cowl made from Bob's original, complete with seam lines, cutouts marked, is available for $49.99 from The Hobby Barn in Arizona. -
http://hobbybarn.com/products.php?cat=112
He mentioned it in his build article.
I have one, and it's epoxy glass, and really excellent.
Remember too, that a Balsa USA Cub is quite a bit wider (more than an inch if I remember correctly) than a Nelitz Cub, so a windscreen might need modification....
Cheers, Mike