I don't know if this would be something you could try or not, it just came to mind when you mentioned that you were having problems with him chomping, and it might be something you could work on when you aren't hunting to help with the chomping issue (I've never trained a hunting dog before, so I don't know if it would actually work or not).
My barn manager and I were discussing last night that she watched a training challenge once where you had to train your dog to go retrieve a hot dog and bring it back to you whole. She said she tried it with her sheltie once, and on the first try he brought her back 1/2 a hot dog.
You might be able to work on something like that, and work up to where he will reliably bring you back a hot dog without mauling it, and then switch over to bird wings (I know there are training companies that sell them with feathers).
If you look into books on training gun dogs, I know I've seen different ideas listed in the ones I've read on how to get dogs to carry birds carefully (I can only remember one method that I've read off the top of my head, and it seems like a cruel way to go about training a dog to have a soft mouth- so I'm not going to suggest it).
Hopefully the hot dog thing will work for you!