I have an old feather flex turkey decoy I do not use and though about trying to use the spray foam/gap filler junk to make it a 3d target. well works GREAT!!! let it dry overnight presto 3d target!

I did the same with a couple cheapies, worked good with field points but broadheads sometimes zipped through without a backstop and damaged a few feathers. Probably me not being patient and letting it dry a little at a time for a denser fill. Those commercial turkeys are a little expensive for my budget.

Way to recycle .    
That works good with old sports balls too .
Like socker balls , basketballs ect...

If they are hollow on the inside, could you cut one in half, Vaseline the interrior zip tie it back together and then fill it, cut the zip ties pop out the foam and reuse the "mold"?   I am unfamiliar with turkey decoys so this might just be imaginary engineering.

Msturm