I've got one, but I built it as directed. As I recall, the deck girders are assembled out of flat parts, so effecting a skew shouldn't be too much of a challenge. Keep in mind that as you skew the decks, the span to accommodate a road below will be reduced. You've probably already thought of that, since you mention needing two kits.
I suggest you get your hands on some Central Valley bridge parts to build a central trestle in the middle if you're going to have two sets of the steel span. The webbing looks pretty good in that application. I'll try to dig up a photo...
Lee