I have been reading on here incessantly about the correct way to size suits, and I think I have most of it down. However, the differences in jacket length is very confusing to me. Some 38R's are 29, 29.5 " long. Some are 31". The same goes for 40's. Can someone help me understand why the large variation? Is it the cut/style of the suit? The "it should cover your butt" rule of thumb doesnt make much sense to me, when I find 40r's with 26" sleeves that only have a 29" jacket length.