"I figure with the center owner sending extra fabric is fine, as that is never going to be more than the finished top, and it will get used up along the way. But I totally agree with the round participants not sending on additional extra fabric unless they mean it as a gift to the next person in line, to use or keep as they want".
I totally agree with this. You can fit a lot of fabric in those flat rate bags and a little extra is not going to make a difference. It will get used along the way and if not there will still be room. An example is the Boom blocks, 19 - 12 1/2" blocks, all in zip lock bags ,they all fit just fine. 1 bag, 1 price.