Slot receivers are really their own position, and height isn't nearly as important as on the boundary. In fact it's probably detrimental just because of physics, they need to be balanced and quick. Good slot guys would be like Percy Harvin, Wes Welker, Danny Amendola, Davon Bess, and Victor Cruz. These guys are running routes in the same space as a tight end so their skills should compliment those of a tight end.

This is why its so hard to find a good slot cornerback. You need the size to match up with a tight end, but need the ability to change directions to cover a water-bug type receiver like Cobb.