This is my first posting, I have been making fishing rods for about two years. I am attempting my first feather inlay and I could use guidance. some research calls for Pearsall's Gossamer rod whipping silk as an under lay. Looking at the cost of this item, I would like to use other types of silk (fly tying), is this acceptable? Or should I just bite the bullet and spend the extra money.

I have put feathers on regular ol' rod wrapping thread and have put it on silk thread with no issues. It doesn't have to be on Pearsall's Gossamer silk. You could put it directly on the rod if you wanted although I prefer to lay mine over thread. IMO you don't have to "bite the bullet" and spend the money.

As I see it, the only reason for putting an inlay on thread is to get the right color background. It can be any thread with a coat of epoxy on top of it to seal it and facilitate laying the feathers and moving them a little in the process.