I must be the most unfit person I know I do little or no training and only try to lose a bit of weight in time for the Manx. I have no experience of doing six laps of the TT course all my Manx GP races have been 4 lappers.
However I have never ever felt any kind of fatigue after four laps except for my fist race when my hands were very stiff after holding on too tightly.
However six laps round Nutts Corner which is less than the distance to Ballacraine leaves me absolutly bloody knackered.
Know I know my TT course speeds are a lot less than the superstars but I'm comparing like with like here.
So I am all in favour of six lap TT's in fact I'd enjoy the challange of a return of six laps Manx GP races.