Dude, I think you're in the clear. By my calculatornations, a 27" wheel is 285.8 mm, which is 2.2 mm smaller than your wheel. 1/10" equals 2.54 mm, so you're within tolerances. The wheel will probably shrink a little once you put some weight on it and ride it, which was probably factored into design. shrinkage may be worse in cold weather, however...