For a professional perhaps, but even than it´s a myth, that muscles derogate, it can be, why do you talk about things you don´t know?
When I hear the term "bodybuilding" I think sculpting your body for competitions and such. Excessive weightlifting, full-time weightlifting? That friend is awful for boxing. Tight muscles may be trained to lift alot, but they are slow to react.
No, it depends what kind of fighter you´re. I´m a little small for a HW (think 5´9 or 5´10, don´t know in American), but I´m big witout being fat, and I´m a brawler, so it doesn´t make me worse when I gain for example 15 lbs after christmas or so, if you´re a boxer who lives because of your handspeed/combinations or so, than it wouldn´t be a good idea of course...
Oh, ****, now I read it, you wrote 81-07, and I thaught wtf is "Relentless" talking about with "Add it yourself"...