Just a thought, but how often will your eggs be turned? Broody hens don't have anything else to do but turn their eggs all day. So, even though they touch, they're constantly being turned which allows them to get good air flow.
If you're hand turning just 3Xs a day, they might be too crowded. If your eggs are on a turned and get moved around frequently, it probably wont be an issue. My biggest concern would be the chicks getting the proper around of air when they all start hatching.
It may not be a big deal either way though. I've seen pictures of incubators jammed full of eggs that had chicks hatching all over the place and pictures of nearly empty bators where nothing hatched.
Good luck! Let us know how it goes, please?