I often run studio days and I think your best bet is to pick a date, message all the photographers on here about the day stating your levels, rates, slots and date and also ask the studio owners to promote it. That's what I do and I find I always manage to fill my slots.
I would be interested in up to 3 hours depending on the cost. I did a shoot at Switch a couple of years ago with IvoryFlame.
Once you know the date, put up a casting call and also get the studio to add a studio day listing. You only need a couple of photographers and you may have 6 hours worth of bookings. So, if you may find you get enough interest to run several days. I have found that shooting at the end of a day after the model has shot for 6 hours is not that productive, so maybe keep it to 6 hours with breaks to make sure you do not get too tired.