Chip

In my experience, creases in mylar and racing dacron dont come out again. It's bad both for shape and the sails usable life.

After having had clear mylar windsurfer sails rip where creased, I am _very_ careful with creases.

In my area, knowlegdeable monohullers roll their racing sails (tape-drives, carbon/mylar stringsails, paneled carbon etc). Or flake them very loosely into a full length bag.
When setting spis, genoas are just pulled down and lashed/bungeed to the lifelines for easy hoisting at the bottom mark, not rolled into a ball (the horror!). The same for sailshifts, old sail is lashed and put into the bag, or just lashed to the rails.

Not to be argumentative, but if I recieved a racing sail flaked and rolled like you described, I would return it as it would have lots of unwanted creases. Beachcat sails are so small that sending them rolled in a tube is a good option. If you are supplying battens at the same time you need the length anyway.