I (24m) am a 6'6" tall fencer (historical fencing on rapiers). And I think that short fencers actually have an advantage over tall fencers.

Yes, tall fencers do have longer arms, but this is compensated by the fact that short fencers are usually quicker and dodge easier. Plus, if a tall fencer aims at the top of a short one, the upper body (or head/neck) is easier to remove from the attack line than the belly. The belly is simply the center of mass and therefore harder to deflect. Plus, the belly is a bigger target compared to upper body parts. And plus, if we're talking about real blades, the belly is also soft and easy to pierce. And a tall guy is usually bigger than a short one, so he's a bigger target - and then there's his juicy belly right on a convenient line of shots for a short fencer.

So I think that a short fencer has more chances and auxiliary factors to stab a tall fencer in the belly than a tall fencer has to stab a short one in the neck, for example.