I once flew with a trainee of such gigantic dimensions in a smallish aircraft (Jetstream 31) that he needed to remove the seat squab, and use a small inflatible childs swimming float which he always carried.
At the other end of the spectrum, witnessed a pilot so small that during an approach in gusty conditions in a DC4, his bum would lift right off the seat whenever he had to apply back stick.
It doesn't matter how well you fit, it matters only how well you do it. (Now there's a loaded statement).
Regards,
Old Smokey