trucatus, thanks for organizing such events... a suggestion if I may.
Seems like there are quite a few who work 5.5 or 6 day work-weeks, and there is a whole lot of people interested (Started off a registration of 12 slots and get 39 responses).
Perhaps make a holding list with all the names, then get people to PM you from the first 15 if they can make it for the next session (12 + 3 reserve) in case they cannot come on sat. That way won't have to re-queue for another fastest-reply-first session =)
Seems like many will be interested in a weeknight session, but understandably getting the studio and stuff as well as running it in the evening will be a little harder.
Cheers.