Hi John,
When you say "VX", I'll believe you're referring to the VX125 from Toyo? Great camera btw

. However, it was designed with sheetfilm users(or with a rollfilm back) users in mind, not MF digital. Although it is a great camera "all around", I think that if you're going to be shooting with MF digital, and need movements(which are TINY!!!! compared to those with sheetfilm), and the tolerances are much tighter, unfortunately...
A guy I assist for has been using a Sinar P2 w/ a sliding back for shooting architecture here in LA, and has had some of the problems you mentioned. Primarily when using WIDE lenses(like that 45mm Rodenstock), even with a recessed(about 25mm) lensboard in place, its still tight

.
So.. you have a few options... you could go with a "tech camera" like the Alpa, or IMO, the much better Arca Swiss RM3d. They don't have the full-fledged movements of a "proper" view camera, but for most applications where those movements aren't needed, they really shine.
Also, depending on your digital back(you say Leaf, but WHICH MODEL), some sensors don't respond all that well to swings and tilts, and can get color casts. This can be problematic, so once you find out if your back is capable with movements w/o a problem of color cast with movements applied, it'll be easier to make a more accurate recommendation.
If I hadn't involved myself so much with my Sinar system for 4x5 film use, I'd have gone with a VX125, they're wonderful cameras(albeit IMO best with film usage

)
-Dan