The brigde below the throttle, is mostlikely the culprit, it takes up about a cm of space, and not all grips are skinny and short, the M8, 3PJ and 3PK all have quite long handles, also the R-1 is what i have now and it has a pretty good contoured grip.

But it is pretty amazing in 20 years they have barely changed their design, also personally i would get a Mars for the fact of its compact shape, is able to be stored away much easier.