There's no room.
I have had as many as eight on my boat(six adults and two kids). I only took this many because the water was calm and they were not big people. Still , there is just no room with that many on board. Six is really about it, but, not under sail. I don't sail with more than 4. There is just not enough room for handling sheets, etc. For just motoring I would take only six and preferably 5 in the cockpit and ONLY with water ballast. I have had no stability problems with the boat. I have sailed it in 6-8 footers in lake Michigan - It wasn't easy because the boat is small and light and gets kicked around by those waves, but I never felt unsafe.