I have a set of commando peashooters on my 77, with mikes head pipes. Mine are off a 750 commando, straight through with louvers inside. Has a very good sound, not obnoxious in any way, sounds like a Norton. The mounting point is not with the channel system, but with two 5/16 nf bolts into two round boss welded to the muffler. I made my own plates to mount them, and it looks very similar to a commando. Back in the late 60's I worked at a gas station in Auckland, just down the street was a Norton dealer. The mechanics would do their test rides past the station, and I would be out there listening to see what was going to go by, Triumph, Bsa or Norton. The Commando was different, had a whistle sound on the over run , really cool sound. But mine don't sound like that, as much as I would like them to. Seems the design must have changed over the years. I have friends with Commandos, and they don't whistle either. The look of the peashooters is really the main reason for them, it has to look like a 70's Brit bike.