@ob this is interesting, to me, as I've heard that David Miller uses 250/400. I also understand that Rossi tightens his laces very tight.
I experimented all winter with hardshells, and with 250/250. I only needed 1 strip each side, and never had any pre=releases (and they seemed to release on any OTF's fairly well).
What @ntx says has some validity (according to Goode's website "THE BINDING IS DESIGNED FOR EXPERT SKIERS ONLY. It should be custom fit to the user and should not be used by others for whom it was not fitted, because it is designed for advanced maneuvers which require increased support and control, even if properly fitted - IT MAY PRERELEASE OR NOT RELEASE IN SOME FALLS RESULTING IN SERIOUS INJURIES TO THE LEG, ANKLE, KNEE, NECK, BACK, SHOULDERS, ARMS, INTERNAL ORGANS, ETC."
When I use rubbers, I use 250/400 and the dual lock never releases.
It seems that using the 250/400 (with hardshells) puts you at extreme risk in any bad fall, where a break or sprain is likely. On the other hand, the increased stability of the hardshell is the asset. Also, the bigger guys have pre-release problems (w/250/250), and have to bump it up. The real question is, how much 400 would a person be using and still release?