Mike Irwin's Peterson Pipe Notes blog and Steve Laug's reborn Pipes blog have dived into this one recently. A bulldog and a Rhodesian are similar in shape. The bulldog has a diamond shaped shank while the Rhodesian shank is round.
I believe post # 410 on PPN was talking about bulldogs, but had links to previous posts that talked about bulldogs, Rhodesians, authors, bullcaps and similar shapes. I have spent hours reading Mike's posts and always learn something new.