As of Dec 12th, 2021:

43 cards to be upgraded (not including proxies)

15 alt borders (to reduce aesthetics of modern frame)

159 modern borders

62 modern cards in a "Retro Border" (to be 64 after all upgrades)

25% is 180, so I'll be under my goal after all my upgrades. Maybe i can reduce the percentage even more? An additional idea is to run some old border fetches, but the Strixhaven Campuses might be better for some archetypes. I need to make sure I don't overwhelm my cube with modern cards, it's currently sitting at 221, which is 31%