My 61 Flash had in 61 straight through pipes apart from the small perforated baffle as stated by Stu, however that baffle was important as the standard check by her Majesty's constabulary was to stick a metal ruler up there until it hit something, if it went right up to the exhaust valves you were in for an earful, then a fine.
If you lived close to me I would come around to your neighbours with my Goldie pipes, (they are loud loud, in fact worries me a bit ) guarantee he would appreciate your pipes after