Our 2012 robot had a large extendable guide to make quick layup shots from the fender. The guide was made of sheets of pink foam insulation glued together and cut with a custom foam cutter that we made. That pink creation was covered in garolite (basically plywood made from fiberglass sheets) to protect the foam, add rigidity, reduce friction with the balls, and give a color we liked more. The whole assembly was very strong, enough that we made a backup but never had to use it, and very light. Under 6 pounds if I recall correctly (but it's been a few years, so don't quote me on that).
Here's a picture of the final product from the back:
http://team1732.com/gallery/var/albu...g?m=1359315011
and from the front, extended:
http://team1732.com/gallery/var/albu...G?m=1362712348
Aaand, another showing off the sleek parabola:
http://team1732.com/gallery/var/albu...g?m=1359314629