11 December 2009 at 4:56pm
(Last edited: 11 December 2009 4:56pm),
I've just come up on exactly this challenge myself. Client wants to sell t-shirts of different sizes and can only add one size (or multiple of that size) to the cart.
There is another (unsupported) module for size/colour variations so will give that a go and let you know how I get on.