I´m pretty sure Schumacher was geared not much longer than Mclaren.he had 6kmh in hand as the official numbers say .
and at least once he had the DRS in use to repass Hamilton.So by the looks of things he hit the limiter 5kmh above hamilton .
As the final drive for monza is a one off item the question is how much scope there is even to fine tailor the top speed ..eg is the 7th gear a direct drive ,are there step gears to further open overall gearing fine tuning.?
Button was geared like Hamilton and started even worse.So the bad starts certainly played a role but you just have to separate the dogs in a fight at one time when they start to bite off the others ears....