We live on our Downeaster 32 which has unreal headroom, close to 6'-9" in some places but realistically it's 6'-5". We lived on a Catalina 27' for one year before buying this boat and there is only 6'-1" headroom under the companionway, the rest is closer to 5'-10" if I had to guess. I could stand up fine, my husband could not. Now I have more headroom in our boat then I do in my office! The building is an old farm house and has very low ceilings on the 2nd floor...
Check out our blog at Sailing Seabird
to learn more about our 32', and MaineLiveaboards | Where Mainers living on their boats can connect.
if you're interested! I am trying to get a good online resource out there for folks who are hoping to move on board in the future.
Good luck in your search!