Morning Ian,
.... my thoughts are towards the Goldie version. My local parts place (Classic Bike Shop in Redditch) do them and also stiock a mute that fits in the end. But I'm nowhere near that stage yet.
I realise you aren't there, yet, but you may find that the baffling inside strangles the engine!
Have a good look inside. An Armours pattern Goldie exhaust that I purchased is so restrictive that the Ducati 450 wouldn't rev above 5,000rpm and the body of the exhaust blued in the area before the baffle!
It now resides on a shelf in the workshop and has been used as a nesting box by a blue tit family.
I have dimensional sketches of the internals of a Dunstall and a Motad design "silencer" for single cylinder engines, if you fancy constructing your own.
Good health, Bill