Where will you park the bike when you are in class ? Folding bikes, especially nice ones as suggested above, are very attractive to thieves and are vulnerable when locked up in public view. You need to take this into account when making your choice, do you in fact need a folder, might you not be better with an old full sized clunker which would be less likely to get pinched ? This has the additional advantage of negating your concerns about your height / weight on a folder, although I don't think that this is really an issue here.