I did my research: photos of western trees, videos on how real saddles are made, and even model horse trees. Normally I would advise tack makers or really, anyone in the hobby to never, but never, use hobby material as a reference. This situation is an exception - I am not basing the shape or structure of my tree on the hobby trees; I'm using the hobby trees as an idea of how the bars should be shaped to work most effectively in our hobby.
I will spare you all the Play-Doh attempts and start with what I consider the first official tree.It was done in Super Sculpty III and is shown in it's current state in the last photo.
I wasn't very happy with the Sculpty. It felt crumbly after I baked it, and I have definite concerns about the longevity of a saddle made with that kind of material. I broke out the apoxy over the weekend and tried again.
You can see on the photo of the back that the cantle is a wee bit crooked, but that can be corrected with a little more sanding. I'm really happy with the sturdiness of this tree - there's a bit of wire in the horn, too. I've handled it extensively for sanding and clean up, and I think this tree can be trusted to go through the entire saddle making process!
Working with apoxy was, uh...interesting. I'd never used it before this tree. I think I like it, though. I used a plastic, purple sculpting tool I have from who knows what for most of the work and water to smooth it. I had a bit left over and did a quick little pony with it, too! He's not quite done but has been very fun.