Mine would be 4.25 to 4.75. They are all reverse calabash, 4 Radice and 1 Thorpe. I love them as they seem to subdue the bite from some of the tobacco’s I enjoy.
My MM 'mini cob' is 3 3/8". I've relieved and ported it to smoke better and it does. Great for a short trip to the store and back, about a mile down the road.
Too close to what for comfort? Do you often accidentally set your pipe on fire? People hold their pipes and never seem to lose fingers, so I'm not sure what the fear here is.