I do breed gargoyles in a group. I watch them very carefully and have an extra enclosure permanently set up in case someone needs immediate separation. I have had to do this twice in the last 4-5 years, but not in over 2 years. I had a stable group of 1.2 together for quite awhile and recently added another female. So far everyone is doing fine but, of course, that's no guarantee.
When breeding season gets going, I weigh each female at least weekly. Most of the time, the female who lays spends several days digging and can be found sitting over her eggs. In the event that it doesn't play out that way, whenever a female drops 5-10 grams overnight, I start looking for eggs. I haven't had an issue with more than one laying at the same time so far (though I did have 2 leopard geckos lay in the same box at the same time a few years ago --see picture below). I did have a gargoyle hatchling appear unexpectedly in the enclosure once 2 years ago but it was late in the season and I hadn't been expecting eggs.
Aliza