Hiya....yep Amber is right. I love my Bio silk sculpts (pics in my gallery if you want a nosey) I absolutely detested them to start with when I trained with Bio first, but then went on a sculpting workshop and picked up a few tricks.
I now generally sculpt with silk, but without a form.
I'm sure Fibreglass will work well too, I shall have to 'steal' some from my Fabric Kit to have a go!
Main thing to remember is flash cure it for 10 seconds to start with and pinch the FE slightly with pinching tweezers and you get a lovely C-curve. It doesn't affect the natural nail but really does help shape the enhancement. From there you can then build you apex and a lovely strong enhancement.
Hope this helps...pm me if you have any questions!