Hi Steve, Roy is a great guy but sometimes a bit idiosyncratic :rolleyes: so he might well steer you my way to sort out for you – se how you get on.. 
Roy is right though you will have to carefully remove the old cans by making a ‘careful’ cut about 3 cm’s up from the original welds and then grinding off the exess – your original downpipes can also be ceramic coated internally & extenally to preserve those – although from my experience the downpipes quickly follow the silencers in the rotting stakes….
Nesarly forgot – the neata 4 into one will fit but needs a section of the lower fairing to be cut away to locate the collector box. I have one in the garage if you want it…?
Cheers.. Glenn