Of course I can't be sure but software control of vcore is quite standar in modern computers and problems appart it is clear that prosperos are beautifuly designed so it wouldn't surprise me if they had it. At the very least they should have it but not exposed in the interface if just because it is a convenient way for them to do a late change without changing resistors. Anyway if they don't have it or if the range is insuficient I would also like knowing wich pwm controller they use ;-).

The psu might limit the oc but I am meaning to go sub 0 and I hope that means a significant reduction in leakage and I hope that it might be enough to offset the increase due to higher frequency (if those things love vcore then we are screwed as the relationship with power draw is quadratic at the least).
Also it would be hard finding more powerful power suplies, it would be expensive and if you have to pay electricity it would be too expensive if it is going to be over 4500W per X3.

I hold hopes of getting answers because it is David's personal miner. And I don't see why wouldn't he want to test it and share the results with us.