Do you have a link to this guy's product? I curious as to what he does to it make it bendable?
As to thinning and kerfing on your horns - have you considered some small shaped blocks to glue into inside of the horns to help lock the shape in and provide some glue surface?
As for the steam box - hell it's a tool! Who doesn't need a another tool in their shop! 
Oh yeah, guess I could have done that before! Here it is:
http://www.puretimber.com/ If you contact him, tell him I referred you. You're going freak out when you see what he can do. It's a compression system he uses and the results are really spectacular.
Here's the instrument wood:
http://www.puretimber.com/musical-instruments-1/We'll see how the bending goes and I'll reinforce if necessary. Again, 1/4" thick is plenty to work with, even if some thinning takes place.
As for steam boxes, I don't mind another tool (for sure!), I just don't have the patience to do this myself. In fact, I decided that if the bendable wood doesn't work, I'm doing the hollowed out chambers on my router table, like the Midtown. Messy, but effective.
My goal is to offer two models: solid or hollow body.
