Why not just leave the saddle as a smart prop with added stuff either as additional spart props or attached with morphs added? It can be more versatile wouldn't it?
Thanks for all the reference images as well a the links, very useful.
I'm guessing you mean to make a new saddle from scratch as a smart prop, rather than rigging one. Out of curiosity I went ahead and presented the classic tack saddle instead of conforming it, and tried some poses with Harry. It actually works quite well so that's something I'll keep in mind. That being said, I don't think my 3d skills are quite there yet.
The funny thing is my background is making props and costumes for classical theatre. I can completely see myself sitting on the studio floor with some foam, an electric carving knife, a 5 gallon bucket and a sharpie on a string, and making something like that, but my brain hasn't quite translated it into how to make something in 3D. That doesn't mean I don't want to make more armor for Harry some day, but for now I want to concentrate on something I know I can do well and finish.