Having just squinted past the set of buckhorns on my 1894c trying to see the paper much less the bull at 100yrds I agree that old eyes struggle and know where you're coming from for sure. I moved in to 50yrds which is a much more likely range for the little carbine, and still had trouble splitting the sight in diamond from the bullseye. It was then that I realized the round front bead is a nuisance at any sort of range.
I still prefer to teach splitting the bull because not all targets are the same size or the same distance. I.e. If you set your sights to hit the center while you aim at the bottom of a 6inch black dot, when you shoot a 3 inch dot, it is going to hit high, and the same will happen on a larger target, hitting low when held at the bottom.
I hit the paper both times btw... just not the center, and I had to push my glasses up.
I just can't bring myself to scope the little .357mag carbine. Even the smallest scope looks like somebody strapped a jet engine on an rc car. I also tried to put a peep sight(gmrs?) on it again. It was never good in low light but I can't see through my old target peep at all in low light now. hence the return to the original buckhorns. Some things are just nicer in their historical clothes I reckon.