Can you be too thin?????

[emsguy]

I want to mount the stock Z51 tires on Cray Brickyard wheels. No problem on the fronts. The rear wheel comes in two sizes I am looking at: 20 x 10.5 or 20 x 11. Trouble is that the stock tires show mounting rim widths of 9" - 10". I would rather use the stock tires and go to a wider tire when the OEM's wear out.
Any problem in mounting the tire on a rim wider than recommended by Michelin?