With a 400-foot lift hill, you're probably going to need more than the "traditional" 2 support structures if you're supporting it with I305-style trusses, only because it has so much more horizontal space to cover. If you use MF-style towers, then there really is no "normal" way to do it and thus any number of structures (spaced appropriately, of course) would work.
I'm envisioning the "hybrid" structure that's been mentioned, and I can't really see any way to make it look good
. But of course, "looking good" is both a matter of taste and rather unimportant in the world of structures.