First of all, great to see this mod back and working. Good Job!

Secondly, currently the mod disallows building a connector inside a factorissimo factory saying you can't build conenctors underground. Is it possible to make it so you can build underground belts even inside the factories?

I tried simply adding the factorissimo surfaces as a valid surface in the base editor source code (surface.name:match("^Factory floor %d+")) and everything seems to work. Would the fact that factorissimo reuses surfaces when the amount of factories go over 100 be a problem?

To be entirely honest I was trying to fix a bug for space exploration that breaks the game when entering the navigation satellite which would crash the game.