OOf, I think I pushed already the limits of what tinkercad can do with 3d designs. Off to learn freecad I guess. If anyone wants to have a look at what I have designed so far, this is all for the fume extractor that I am tinkering with: https://cloud.otherreality.net/index.php/s/3mDXRX4LZ9AsLKM

(Zoom out when opening one of the STL)