I've recently got hold of a second hand board (see other thread) and when I bought it, I knew that one of the fins had been replaced, but when i looked the fin up it appears to be a windsurfing fin. and also 2cm shorter than the fin on the other side.
Can windsurfing fins be used as replacements (they certainly seem to be cheaper!)? I can't notice any cant on the 'other' fin if that makes any difference, it appears to be a straight fin.
added pics: