I have heard of a lot of barefoot trimmers having success rehabing navicular horses, but I have no personal experience with it. This blog page talks about it briefly: Bare Foot Horse
I'm still a little suspicious of laminitis, but I'm overly paranoid about it. I do hope you find something that works for him management wise.
PS: My love of barefoot trimming doesn't mean it's the only way, but I have personally had very good luck with it. :)