From my own experience I've found it's impossible to predict where you should be unless you have some prior information (e.g., if you've found you're ideally at +0.5 on an MX88, and if there's also a consensus that people should be mounted similarly on both the 88 and the 83; or that you've used a certain method, say BOF, on comparably-constructed skis and found it works for you consistently).
In the absence of such additional information, I think you may have only two rational choices:
(a) Mount at the factory line (in the absence of further info., this is probably the best bet -- sort of an Occam's Razor approach);
(b) Get an adjustable binding.
If you do get an adjustable binding, I think either a Marker Griffon Demo or an AAAttack Demo would be your best bets -- I believe these are the only demo bindings that are comparable in performance to their retail counterparts. Another alternative would be to get a plate + binding system that allows you to move the binding on the plate, like the Head PRD (easily adjust position by 4 mm) or the Vist (less convenient -- need to unscrew from plate and reposition).
Edited by chemist - 10/4/15 at 5:51pm