I just ran a few tests here with my impaired vision. Just some in-sight
, I'm near-sighted which means I can see my guitar great, but things start to get blurry a little further out. I'm over the century mark, and have ~20/50 vision. When I put glasses on I get the effects of presbyopia kicking in which means everything about 3+ ft out looks great, except I can't see my guitar anymore.
When I invert the text using the HOLD function, I find it to be harder to read than the default text. I think it's because there is still a bright border around it. Perhaps if it was fully blacked out it would be better, hard to say.
Looking at the unused text spacing on the FC-12 leads me to believe if that was filled up with bigger, bolder text it would be the perfect fit for me. Seems like there is definitely room there to grow the text for people like my self.