After a lot of Google research
, I settled on a Armours siamese system to fit a '54 RR new build. From what I can gather ,they use thicker wall pipe and are triple plated. Price was OK in comparison to what is available in Australia , freight was a killer though.
Anyway I bit the bullet and ordered them, arrived about 10 days later packed well and looked fantastic. The RR is still on the bench so I fitted them to my '60 Super Rocket for a trial run. Fitted straight on, no fettling required, secured the header pipes in the head with some silicone type sealant and fired it up. A little louder than my twin stock pipes but a deeper sound.
Since then have racked up about 400 klm of spirited riding (70 mph cruising) following a few "moderns"with no issues of headers moving in the head, chrome is just starting to yellow at the pipe junction.
So very happy with them. Hope that helps.
Don