if you have an accurate fence that isnt a problemif u have ur front back and sides, cut them ALL AT ONCE! u will NEVER get the same 13.5 inch or whatever everytime. u will never be exact 100% of the time. if u are 2 mm short, CUTE EVERY PIECE that should be that length if possible. cut a 48 inch piece at say 13.5 that way, u can come back and cut it at the length u need, and all ur pieces are the EXACT same height.
if you have an accurate fence that isnt a problem