I eventually ended up with the file above as the shape I wanted for my vertical pillars, but I don't think I can 3dprint that, as the bottom end will not build up correctly. If I stand it up, the middle bit suddenly goes out over thin air

The best idea I had was this The sketch tries to show 2 pieces (one in construction geometry) which I would have to glue together as shown for the middle bit to get the 'wrap around' effect I'm looking for. I'd glue full circles on to them, but all this is looking very messy and gluey. The pillars have a 16mm diameter. I'm hoping for a better 3d printable way of doing it.