There's a lot of info on here about that very subject, but I can't recall exactly which thread. If you do a search here, you'll probably find a lot of stuff on this very subject.

Not trying to be a wise-guy, but i've already blathered on about ad nauseum, and I recall a few others did as well.

Basically, uprights have the piano case flipped vertically, and you have some different issues than a standard grand; distance to/from the nearest wall is critical, and mic'ing the top & bottom is important as well.

There's no lid as such, so you're going to get a whole different set of overtones than you would with a grand. Those thicker /shorter strings sound weird too. You can't cheat the laws of physics, but makers of spinets and uprights keep trying.

Good luck hunting this one down, there's a lot of good info here, as I recall. If not, check back and we'll hash it all out again. 8-)

As Joe said do a search. But a couple of quick suggestions. (1) Move it into the room. Not the center. Try about 37% of the way from the wall. Use the golden ratio if you want to be precise. (2) Start taking it apart. Take off the panels that cover the strings. This will give you interesting new paces to put your mics

There are a ton of options and the best will depend on the piano, the room, the mics, and the player. But this will give you something new to try.