You won't know how much a 305/40R22 rubs until they are actually on the VX. However, the front wheel-wells of the VX is extremely tight and cramped, and anything bigger than your current 285/35R22 is gonna require major surgery.

I know your goal is to get a bit more sidewall rubber to soften your ride, but it's not gonna improve any with the 305's either. It will be just as stiff, with the added headaches of more rubbing.

My very best advice is to just stick with your current set-up with the 285/35R22 and possibly consider changing your shock absorber set-up for a more softer ride. Your speedometer is dead-on acurate with the 285/35R22 (29.9" O.D.) and won't need to be adjusted (see Tire Calculator at Discount Tire website). In the meantime, avoid hitting the potholes and pick streets that are a bit smoother. The VX is naturally stiff due to its short wheelbase, and gas-shocks. Again, stick with your current set-up with the 285/35R22.