Alt-mode rendering is very slow

[Fobax]

I've got a fairly large base (~1 rocket/min) from 0.16.51 that I stopped playing because the game was very slow. I just loaded it in the latest 0.17 hoping it'd be faster, and realized the problem is alt-mode. When standing in the middle of a big swath of bot fueled factories I get I get 40/40 fps/ups with alt-mode off but 11/60 with alt-mode on. Alt-mode off is pretty hard to play with given there's little to indicate where I am in the factory. With alt-mode on it's unplayable since it just stutters terribly, to the point that even my mouse cursor is hard to aim.

This is playing 0.17.17 on a AMD Ryzen 5 2400G, no discrete video card, 16gb ram, and at 4K (40" 4K monitor) on Ubuntu 18.10 with a 5.0.1 kernel, launched through Steam.

[BlueTemplar]

Sounds like we might need an option "do not show bot 'contents' while in 'alt'-mode" ?