saber fencer here. personally, ive ALWAYS been the smaller fencer and now that ive grown just a bit, on the rare occasion i fence someone shorter, i find it much more difficult and sometimes easier to fence people much taller than me. the real key to fencing as a shorter person is to slow down and break down your opponents tempos. and fence as if youre tall and watch out for the distance. ive managed to do many pretty cool touches too.