I bought a pair of size 13s in 1979--they were great, and I used them until they wore out. My memory of them is that they had a slightly negative heel, which seems to not agree with the OP--maybe I misremember. One thing I do vividly remember is wearing them in a 4-mile road race (running race) with my girlfriend at that time because I didn't have any sneakers. It was a fund raiser of some kind, as I recall. I hadn't run in years--since cross-country in high school--but I was in pretty good shape from commuting 25 miles to work each way, so I was pleased to find that I could move right along. I remember that I was exactly the median finisher--number 216 out of 431 or something. The next day my legs were so destroyed I could hardly walk--had to come down the stairs backwards.
I'd snap up a pair of BBs again if I could find them in my size.
JV