Prusadollo progress: as I don't have the original aluminum bed carriage, I designed printable version based on the original. Of course it should be quite stiff so I printed it with ColorFabb XT-CF20 carbon fibre filament. Result is quite stiff, especially since I used 0.8mm nozzle, 3 perimeters (2.4mm), 1.5mm top and bottom surfaces and 25% infill. XT is bit finicky to print since it likes to stick to the nozzle and leaves blobs in random positions, so I had to babysit the print somewhat. Also had a fail when trying to print with 0.15mm layer, the material just wouldn't stick to the previous layer. Ended up printing with 0.25mm layers (KISSlicer synamic layers 0.25-0.3) and the result is more than good enough.
XT's glass transition temp is ~80C so I printed the corners with ABS, so that the heat from the bed should be ok even when heating the bed up to 100C. I do have insulation under the bed PCB, so XT should survive fine.