This can go a lot lower, I feel, but sub 43 was a good first goal for some time. I accidentally erased my original splits, so that's kind of a bummer, but that's a first sub 43 run.
Zero Project has some unfortunate flaws in a speedrun context, but it's still fun. Zero has some more movement options than X in the vanilla game, and while it's annoying that the end game as Zero lacks a quick kill weapon, the added challenge is also a nice thing when everything goes right.
The Sigma fights, in particular, are a big threat every time.