Jes-
call around and look for a used windsurfer mast- I got mine for 100$ (which, I guess isn't cheap -in the strictest sense- but this is much less than the 350 or so they cost new). I am not sure the aluminum is better/worse than carbon fiber however. I don't see any reason why you would have to shorten the forestay/shrouds or have to modify the jib.