We are a lightweight crew in a boat that is said to 'carry weight'.  Is that a benefit for us compared to a heavier crew sailing the boat, or us sailing a boat for lightweights?
 
The usage is river racing rather than open water. 

Which design are you talking about?  If you are river sailing the "weight carrying" designs will have more rounded sections and more rocker (to give the extra displacement on the same waterline length) which is exactly what you want.  Where you will miss out is in planing performance, not that much of an issue for river sailors in my experience!
 
Andrew 3511 & 3088 

Hi Andrew
 
That's helpful.  Our boat is one from distant Merlin history and a Holt Martine design - I have been told a couple of time 'ah yes, designed to carry weight'.  My crew and I do not carry much weight ourselves but, as you suggest, are rarely overwhelmed on the river.  
 
I only put the boat back on the water a month ago (after she was in a boatyard for 20 years)  and the point of my question was to understand more about the hull shape and where we should be putting our weight - esp in terms of fore-aft adjustment.  
 
It does feel like she bobs across the water (as opposed to slicing through it) and maybe that is the effect of the extra displacement?  
 
I have no complaints about performance relative to others in our fleet and we're learning from every outing.  Great fun.  

There's a shortlist of designs that river sailors value most, with the Holt boats Passing Cloud and Martine the oldest, then the Proctor boats IX, IXb, XII, then in the next generation the Morrison Satisfaction, Smoker's Satisfaction & NSM2.  The rocker in the early boats helps reduce wetted area in light winds and keeps the transom out of the water.  Enjoy!  BTW if you want to know more, Dougal Henshall's book is well worth buying