When megaprims are used in a sim, the Mini-map does not render their area correctly. For example, a 5 M high, 60 M long, 0.1 M thick wall looks like a 20 M square on the mini-map, while it should look like a very thin 60 M long line. In many cases this means that an otherwise well-behaved megaprim blots out visibility of much of the mini-map.
Requested change: Either render megaprims as taking up the correct amount of area on the mini-map, or do not render at all on the mini-map any prims that are over 10 M in any dimension.
Saying that, this could be a open source patch if some one was annoyed enough by it and had the free time as this is just a viewer display issue on the minimap.