I have mastered the art of stuffing the flat rate envelope. I've gotten 8.5 yards in one. It was bulging at the seams but I wrapped that baby in tape. I've heard that's against USPS rules but they let me send it. I've also stuffed 29 yards in the flat rate medium box. My biggest achievement was 9 yards of minky in a large flat rate box. Big thanks to the hubby for helping with the origami folding to get it in there. I have to say...it's all about the folding. Just practice folding...you'll get it!