For a clean cut i'd go with a plumbers tubing cutter. Probably not something you would buy just to shorten your handle pole tho. Most everyone has a chop saw or sawzall-or know someone that does
Just wanted to mention that I successfully cut my tubes 3 inches with a tube cutter, AND... I didn't have to disassemble the whole pole!
Worked like a champ, took off the clamp bolts.. pulled it apart then taped up the ends to protect. Used a dremel with cutoff wheel to cut across, then spread with a pair of pliers to release cables.
Almost zero chance of cutting a cable, if it concerned me I could have sandwiched the cables with some dowels, but cutting from the top it's pretty easy to see where your cables are, all 4 came through unscathed.
Whole thing took about 10 minutes, my arms were a bit sore though lol (took about 30-40 turns each tube) Mine was just a cheap home depot cutter, probably not the best blade as they're typically used for copper or PVC.