Oh wow. That’s not something that I’ve seen before. If anyone can help, please chime in! I’m sure the plastic is less flexible than the standard caps on a ProFly. I don’t want to tell you to force them in and have them crack. You could go to the source and contact John Higby himself. He’s a very nice guy and has replied to my messages before. Go to his site and send him a message: Contact / BigYoYoArt