I just called Hobby Lobby. Because I bought these Kavan 10x4 Softprops from my local hobby dealer instead of directly from Hobby Lobby, they aren't willing to replace or refund without going through my local hobby dealer. It's not what I was hoping for, but I'll admit that it makes perfect business sense.

The next step is to have my local hobby dealer contact Hobby Lobby to find out if they can get the props replaced or the money refunded.

In the mean time, I have boiled the remaining 10x4 Softprops for 30 minutes to see if that will help soften them up.

UPDATE: Boiling didn't help. I broke yet another 10x4 Softprop.