275's are the recommended max width on the stock rims, though several people (me included) are using 285's. Max height? depends on your goals - do you want the speedo to be close to accurate? If so, 285/55's are best - a lot of people have also used 60's, which are about 1" taller IIRC, with no problems.
If you don't care about speedo accuracy/gearing, then it comes down to how much cladding trimming you want to do. Someone here with experience in that department will chime in to help, I'm sure.
The 285/60 or 55's look like what should have been on the VX from the factory. They extend out to the edges of the wheel wells, and from the back or front give it a much sportier stance. The ride with these wider tires is rougher, and the VX tends to follow ruts in the road. While those two side effects could be related to my choice of tires (Scorpion Zero's), I've heard others mention the rut problem with other brands. Neither are a big problem IMO, and definately worth the trade-off for the much improved looks.
"If you're not living on the edge --- you're taking up too much space!!"