Hmm - I haven't bought felt by the yard except for a Christmas tree skirt - will have to try it. I have used the craft felt squares to test-sew embroidery designs and have found that as of late it seems to stretch all over the place and come back to shape with a little steam. Will have to try some yardage and see.
Your idea sounds great to me as a filler - will try it.
Marysewfun