I guess for a short trip it's probably no bother but I worry that doing similar will eat through the carbon in pretty short time. (Good excuse to buy that newer fork though :D)
I've been thinking of something like this for a while now, coupled with a bag with a fairly stiff backpanel. Wrap of inner tube between the clamp and fork for some grip and paint / carbon protection.
I zip-tied a crappy bottle cage to a normal steel fork on my first tour to carry 1 litre of methylated spirit. Lasted 6 months.