"Me, I'd buy a Brocock Super Six Contour XL and a handy 500cc filling kit from best Fittings and pocket the difference."
Westy306 did do a lot of research in to the FX and for that matter in to the Super six contour XL which I'm seriously looking at now as my budget is smaller. I have yet to have a go with the FX but will no doubt be impressed with it.