My eyesight is getting pretty bad too, but I improved my Krag performance dramatically by opening up the Buffington rear sight notch with needle files, wider and deeper. Another thing, on all iron sighted rifles I concocted a Vee aiming point like the old NRA and Military targets of the period prior to WWll. I use buff or white paper and a large home made stencil with blue or black V about 6" tall. I hold a sliver of white with the V almost resting on the front post, great contrast for old eyes. The rear notch now, with the rifle in the shoulder, appears to have about as much daylight on either side of the front post as the post's width. My Krag is not a collector, so I had no problem with altering the rear sight.
I once owned a sporter Krag with a 2.5 Weaver in a true side mount. The scope was about an inch to the left of the bore centerline, I guess to facilitate ejection, extremely awkward, I never got used to it and it went down the road. One man's opinion.