I’m doing a bunch of test with the default ini.
I’m getting much better results with a low static lighting level scale (From .8 to .1) than any other settings. I’m even leaving lighting quality to 1, smoothness to 1, bounces to 10-20. I set my lightmaps res higher/uncompressed and I’m getting better results and faster!
Time to reconsider my old workflow I think. (for skylight-lit only scenes, at least).
Quick test for the indirect lighting quality alone. Lightmaps res are 1024, scale set to .4
Quality = 6 (4mins30sec build time)
Quality = 1 (1min32s build time)
Not a huge difference imo. build time is a lot higher with 6 tho.
Static lighting level scale alone now (with indirect lighting quality set to 1)
Scale = 1 (1min13s build time)
Scale .4 (1min 32s build time)
Scale .1 noticed the extruded lines on the walls receive some shadowing 
3mins19s build time tho.
In this scene, it’s clear that the best setting is the scale.