i have been kickboxing and boxing for years and heve always been shorter.1 use side movement,if you only move forward and back they can dictate distance.moving side to side makes it harder.when they throw a technique follow it in.Every time you block or slip when the person is bringing back their leg or hand follow it back in.But the most effective is angles by using angles correctly you negate all of the reach.One bad thing is if you don't have good movement you have to stay there.so there are 2 choices foot movement or get very good wind so you can stay inside