I would ask one question to counter this… Is there a need to look at the hands during performing?
I’m quite small in nature…still I find no prob to reach both ends at the piano and generally my vision tends to consume more time looking at the painting and decorations of the hall than the piano per se.
I would say also that when I played the piano regularly, I rarely looked at the keyboard. The advantage of the piano is that there is a configuration to the black and white notes that makes it easy to feel your way around. Not so on the harp. I have to look much more at my hands and the strings, probably because I don’t play regularly enough to easily feel distances. If I’ve been away from the harp for a while, the first thing that goes is the ability to feel octaves, chord positions, etc. It comes back very fast, but if I worked as a professional harpist and played all the time, I wouldn’t have that problem.
The larger visual problem on the harp, which was addressed not too long ago here, is being able to focus on the whole plane of strings. Those of us beyond a certain age have an awful time getting glasses that will allow us to focus on the entire range of strings, and usually have to settle for one end of the instrument or the other being fuzzy.