I dunno - I know several Berkeley owners who are well over 6 feet tall and seem to fit. Berks have a surprising amount of room in them - more in many dimensions, for example, than an Elan. But - I don't know how the big guys manage to get out once they're in. The cars are very low and you just about sit on the floor. Phil Curren, who restored that pretty red #13 from a real basket case, is a pretty hefty fellow himself.
The two cylinder cars were slow, especially with a heavy driver, but the 3 cylinder version and the Royal Enfield powered cars were tolerably quick.
I think this Craigslist car was on eBay a short time ago. The nose isn't stock but doesn't look too bad.
I took that picture of Phil's #13 and people keep using it in their ads. I think I'll start to charge royalties.