It's not over until the slightly-overweight rider #68 sings.....
I'm convinced that there is more usable power to come from my 674 for Donington, without resorting to headwork or anything illegal. Things like manifold matching and a change of exhaust should help both bottom end response and top end power.
Ali, IMHO your FCR41s are way too big - even my 39s are excessive given the current valve sizes (but may be useful on a 620 motor...)
Also ignition and cam timing can make a difference, but now I'm giving too much away