Recommended distance between stations

I want to improve the MLAT reception/detection in my area (near the local airport)…

What is the recommended distance between stations to achieve a reasonable MLAT accuracy?
I know that if two stations are to close together, one of them will not count as different data…

1km is the minimum for them to be considered distinct. If they’re closer than that, data from both is still used, but they’re not considered distinct stations for the purposes of the minimum number of stations required.

For the extra stations to contribute significantly to the quality of the solution they need to be quite a bit further apart, perhaps 5km. (Typical pseudorange error is maybe 0.3-0.5km so even at 5km separation that is a large relative error)

So, theoretically… if I can manage to install 4 recievers (one on each corner of the airport) separated more than 1 km each., It should enable MLAT on the ground of the airport??

And the greater the distance between them, the better the acuraccy of the MLAT position?

In theory yes but in terms of the quality of results YMMV; the timing errors with rtlsdr dongles are a large fraction of the distances involved with that sort of setup.