I used to use very thin Tyvec strips, 1/16 inch or so, as an underbody for large light colored flies. For example, the underbody of a large Coffin Fly spinner had the underbody of Tyvec and then I dubbed the body over it. This was not an idea of my own. This was what Al Caucci had us do with his March Browns, Potamantus, Hex's, and a few others. As far as price - anyone can get the stuff for free at the local post office. The 'soft' Priority envelope will yield a lifetime supply based on how we used the material. Other uses may require more materials. Hope this helps.

Allan