After years of stumbling in the dark, I finally came up with a set of criteria that I use before I buy a pipe. Almost all of my pipes are group 4-5. I also have a couple of group 6's. I buy pipes based on the tobacco I smoke. I smoke nothing but flakes or plugs or a rope. I have 2 aromatics that I smoke when mom visits. She like either one as her father smoked a pipe for most of his life.
My criteria is pretty simple.
Bowl height around 2"
Inside bowl depth 1.5"
Inside bowl width .82 is my favorite .75 works as does 7/8 on the right pipe.
I don't know the numbers but I like thick walled pipes that weigh 40-55 grams. I do have a couple of holders but I clench almost all the time.
Almost all of the pipes left in my collection after my culling are pipes I consigned. There is just something special about working with someone who sees pipes the way I do. I only have classic shapes in my collection. I like mostly straight but small bends are also fine. I don't do full bent. The shapes I own are Billiards, Dublins, Apples, Rhodesians, Lovats, Bulldogs, one Volcano and I can't think of any others. Some would call it a boring collection, but for me it really works. I will be adding some more pipes and they will fit my collection.