hi again,
thought i'd look at the tail conversion on my bike today, just for curiosity sake and to see what i have missing under there. I thought that the subframe looked robust and roomy enough move the essential bits around and cos it's a big bit of steel there is plenty that could be cut off.
i was a bit disappointed that the rear pegs/exhaust hangers are an integral part of the subframe, as i would have liked to remove mine for some aliminium exhaust brackets.
i think providing the tyga plastics are the same length as the 16 plastics on the 16 and the depth and width of the subframe is similar between the 18 and the 16 then you should be able to mig weld up some decent fixing points. if i was going to do it i'd get a cheap subframe and keep my original just incase it goes tits up. somebody on this site must have done this already and now doubt they'll let you know.
wes