I had a 21' cabin cruiser sailboat that weighed 2500 pounds and it rode on 2x4 bunks.  You'll be fine.

Oops, just saw the second question.  Your hull should be entirely waterproof, so no need to worry about sitting on wet bunk carpet for a few hours.  The damage comes during the trailering when all the friction happens.  The water may actually help at that point.  I wouldn't worry so much about the bunks.  I know you've put a lot of effort and money into it, but we have tendency to be over protective parents at first.

   Thanks for the reassurance.  The wider bunks have to be ordered anyway, and I'm ready to get the boat in the water after a year or working on it (not counting the months  of delay because of New Hampshire winter temperatures!).  My thought about the boat resting on wider, wet bunks was more of a concern about the extended contact with the paint (Brightside Poly...) while the carpet dried out.  That paint is officially not recommended for below the waterline - - but we use it anyway, especially in circumstances where the boat's in the water for a relatively short time.  So maybe my real question is whether wet bunks of any size have caused anybody problems with the paint after repeated times of sitting on them back in the garage.