I use spray and 80/20 batting all the time. works great. I don't even have to pin.

I love the 505

I spray baste all my quilts and use the WalMart cheapo I think its made by the school glue people. It gives directions for permanent or temporary spray. I use the temporary method. I have used it on QFK and it washes out, no stiffness.

i've used the 505 spray on poly batting and never had any problems with it holding. no matter what kind i've used i have had to secure my edges either with pins or basting for added security around the edges but other than that it has not been a problem with the poly batts; maybe your spray is old? may need to shake well, and spray liberally.

I have used poly batting and basting spray. No problems here.