I have been recording my upright using ORTF after testing several other options. I liked it the most for the reasons CyberGene mentioned before. IMO, it provides the best stereo image.
I have been mostly closed-miking the piano, so I run into the same issue you point out. I use a MP of Rode M5's , and I bought them together with only one mic stand, and the Rode stereo bar, which allows me to mount them together and even has marks to place the mics accordingly in ORTF, A-B, and 90 degrees. Rode stereo bar
I though I was all set up until I notice I could no manage to place the mic stand in a way that the stereo bar is then parallel to the piano and at an angle that the mics can point towards the strings. The stereo bar will always be orthogonal to the mic-stand arm.
So I bought this (very affordable) beauty:Quick-Tilt Ball-Joint Microphone Adapter
which I attach to the mic stand and allows me to move the stereo bar freely in all possible angles. I then turn the bar upside down, place it parallel to the piano, and adjust the mic clips so I can point the mics towards the strings. You can see how the set up look like in this video of mineSetup
For me the issue sometimes is that the mic stand can not support the weight of the whole setup (mics+stereobar+adapter+mic clips). I wished I had bought a more robust mic stand. I go around it by using the mic cables to counter balance the setup weight.
I hope this helps.
Ps: all videos in my channel since March have been recorded with this setup incase you want to check the output. No much audio-post processing going on. I hard pan the mic input. In my very last video
I place the mics above me to avoid the damper sound, which was a bit too notorious with close-miking.