Got the frame stabilization done for the Dollo.2 build. It's quite rigid now. Printing all the screws, beams and center parts took quite a lot of time and material, so not sure if it's worth to do the stabilization with plastic when same thing could be done with threaded rods. But for science!
For the models, I also did some experimental internal infill magic by adding 0.1mm holes through the bolts, beams and center parts. The idea is that slicer has to add extra parimeters around those holes, thus making the parts stronger. I have no comparison to parts without the extra infill features, so how much it helps is just a guess.

To test the stabilized frame, I printed yet another vase, 330mm in height. 0.6mm nozzle, 0.35mm layers, 2 perimeters. The quality is quite good almost all the way, but at the top there's slight banding, which I think comes from the z-screws that aren't secured at the top and move around somewhat. But marked improvement to the previous vase, that showed quite bad artifacts due to the frame shaking around.