I got my pool noodles from the W big box store for 97c each and they're already pretty long so how many you need depends on how big the quilts are that you normally make? You could always cut them to make shorter sections to join together. You're supposed to stick some PVC pipe in them to make them completely straight because they're kind of bendy with nothing in the center. You can also have the PVC cut into sections so that everything is smaller sections and you can join them to the lengths that you need. Would be lighter than boards, I think?
That being said - I was in too much of a hurry to sandwich and I used the handle from my Swiffer mop to join the noodles together
Yes, it was kind of bendy, but I made it work and it was still pretty easy! I'll get the PVC when I have time to go to the hardware store.
I've read about basting with water soluble thread so that you don't have to unbaste anything when you're done. It sounds fantastic.