I think if Napoles could comfortably make 140, which is possible but unlikely, then he dominates Chavez over the distance and tames him badly.
Napoles actually DID fight at 140 for awhile, until he moved up and whupped Cokes. I'd say he was more natural at 140 than 147.
Napoles was a small welterweight... most of his career bouts occurred 135-140... he went to welterweight because that's where the money was