- 3,474
- 2,815
I've shipped most sizes up to size 12, and yes I am altering the box. I only alter the boxes when I ship to Cali, Texas or Florida and the package weighs over 2lb, otherwise I use regular shipping boxes. The med flat rate box can fit those XI slide out boxes perfectly (up to a size 9.5-10 I think).What size shoes are you shipping? and are you altering the box?