I have 7800 on Dec 8 without moving the base (an without storages, mortars, reactors, drones). The trick is that you have to ignore the left part of the map, build one laser left to your base and defend this choke point. Only expand east and south. Use mortars to controll the south-eastern basin and do not overbuild.
My house rules to get a better challange:
- it is forbidden to move Odin city
- no storages
- no drones
- no reactors
- no on/off switching of anything
- you can move mortars and blasters only to places, where they are connected to the grid
It looks like there's a bug with it, i'm looking into it.