Hey James,
I have Toyo 275/55 R18's on stock rims. My VX handles fine. I guess I noticed a little difference when I first got them installed, but now I don't notice any severe issues with handling (no severe pulling or cornering issues). Maybe you should keep your tires on for a little while to get used to them. or switch back to 18's and get the 275's. Seems like some pretty expensive Rim/Tire package of your's to give up on so soon!! Just thought I would throw in my $.02.

Adam