Our meetings range from fifteen to thirty-five people, on average. Most groups here, especially the ones who have meetings on the larger side, ask that "you keep your sharing brief so that everyone who needs to has an opportunity to share." My home group asks for no "double dipping" unless everyone has had a chance to share once. I've even heard of groups that use timers.
Bottom line, what does your group conscience decide as a guideline for sharing? Just say that, and I'm sure you'll be fine.
Peace & Love,
Sugah