I really don't know if PVC pipe would survive the treatment that Sorcha describes.

An alternative would be to buy a suitcase of suitable size (one of those plastic ones with rounded corners) They only cost a dollar or two at thrift stores
get a couple of cans of urethane foam
spray the bottom of the case and cover it with polythene film
press the bows into the film just a little while the foam is still wet
cover again with another sheet of polythene
spray on more foam and close the lid