My guess is all the fashionable people don't want red bindings because these bindings are lasting outrageously long. They would look really tacky on my green B4s so I might swap them out with the black pair I currently have on them.
How good a match would the 912 be on a pair of Volkl Mantra's?
Personally, I think the lift on the 912s is an ideal height for fat skis. (Other people prefer a flatter mount.) I have 912s with the same lifters as the bindings you just bought on my B4s and Pocket Rockets. The only problem I see is you'll have to pick up some fatter brakes somewhere.