Yeah, BJ is always bitching about cutting, I really don't believe he's a natural FW, he's outsizes several lightweights and walks around at WW.
I say nowadays a 'natural' to a weight class is someone who walks around at the weightclass above, although I do know that many hang out at 2 above, it still isn't 'natural'.
Anyway BJ Penn ain't cutting to FW anytime soon, and I don't think its fair to guys like Frankie Edgar, Jens Pulver, Kenny Florian etc. to say BJ is comparatively light for his class.
BJ is a hall of famer in terms of legacy, nowadays you can still call him 'elite', but not in P4P contention (Fitch outcome notwithstanding)