The problem with collisions may still be hidden in the exporter, for example, YABEE uses the egg format, which leads to the following: all polygons are converted into triangles when loading. And this increases the calculation by about two times.
That’s true, but I don’t know what proportion of triangles to quads my room-floors actually have: they’re often not simple rectangles, and so tends to include at least some triangles in defining their shapes.