For starters I have also never tried this, so everything I say is pure speculation based off of pictures.
For your situation with a 2027TR-HTRF+ I think you'll have a tough time as your motherboards have microLP slots which means the screw layout is at least a little different and you'd need new rear windows, which might be very hard to get for the individual nodes. There are X10 boards with the slot, but they are meant for FatTwins and have a different profile.
If you had a Twin with standard PCIe slots the screw layout looks very similar between X9, X10 and so does the layout of the rear IO so it's possible it could work with minor effort. The connectors for the midplane riser look similar, but I'm not sure they're the same.
The X11 board that shares a similar profile and screw layout seems to use a different connector for the midplane riser so you'd need to validate if conenctor from the riser to the midplane is the same as well and source risers on top of motherboards.