I have Kirsten's table, Molly's old wooden dropleaf table, Sam's wicker table and Felicity's table. I've bought an extra chair for each set and can fit 3 dolls fairly easily around each type. I also had Molly's new table for a while but didn't like it so I sold it, including the extra chair. If you include either a teapot or a floral table arrangement, it's a pretty tight fit with three full place settings on any of these tables. I usually put the teapot, cake or whatever kind of food is being served on the 4th "side".

From observation, I would say that how many doll legs you can squeeze underneath a table depends on the state of their joints. If she's a new doll with tight joints, she'll need more room than one who doesn't mind having her legs pushed straight out ahead of her.

One solution I've used for slippage and legroom problems is to have each doll keep her left leg on the floor and fit only the right leg (and corresponding sit-upon area) on the chair.