Frustrated with AF in studio - what are your settings?

First of all, I'll say that I love the resolution, color, and overall organic look of the 42mp files from the A7rii. At iso 100 and f5.6-8, using the best zeiss and GM glass, the sharpness is incredible. This is a shot from some light testing I was doing last week with a friend (GM 24-70 at 70mm f7.1):

That said, the AF in somewhat dimly lit studio situations is horrendous compared to the Canon 5DM3/4 that I occasionally use. I've tried everything (a lot of it from helpful threads here in DPR) and it's still just on the bare edge of acceptable unless I have the lights up almost all the way in the studio.

I shoot with an A7rii, and primarily the GM 70-200 f2.8, occasionally (quite rarely) with the GM 24-70 f2.8, GM 85 f1.4 and Zeiss Planar 50 f1.4 in a studio setting as well, and have had the same AF issues with all of them.

Camera settings are typically:

• SS 1/200-250
• f5.6-8
• iso 100
• Focus mode: AF-S
• Focus Setting: selective spot medium
• Live view display: setting effect off
• AF illuminator: off
• AF drive speed: fast
• AF track sensitivity: High
• Face detect: off
• Priority Set in AF-S (and AF-C): AF
• Eye-AF: generally not used unless in a studio setting

Curious what others are using in terms of settings that have helped with AF performance. In particular, I'd love to be able to make AF-C more reliable, as I've found that in lower light situations, it locks focus less reliably and accurately than AF-S.