Well the single cylinder ran in the UK - probably the weather here helped
On a different note I am pretty sure that tires have nothing to do with the vibration issues they are having (though even honda people seem to hint at it). I know from experience that tire torsional frequencies are VERY low and unlikely to interact with anything else in the driveline.
If it's gearbox related you can't blame Mclaren either.. the engine is one big inertia, the gearbox is another - stick something soft in between and it starts dancing.
So far nothing said in the press has indicated rectilinear vibration - it all appears to be torsional.