No problem with cutting off the excess - have to do it all the time when building up dual suspension Y frame MTB's to sell! I use a pipe cutter with hardened steel roller blades, then file/grind/sand a nice smooth rounded edge on the cut end. However I really wouldn't bother just to save an ounce or two of weight - the saving is lost the moment you fill a water bottle or carry stuff in your pockets! If you do cut it, make sure there's a minimum 4" (10.6cm) of seat post left in the seat tube.