It all adds up, but...
Conventional wisdom is to keep the weight low and in the middle of the boat; however, to tweak things a little bit, watch the water at the stern of the boat.
Some boats are designed so that the transom is above the waterline and as the boat speed increases the boat sits lower in the water. For example, the typical '30s boats had long overhangs so as speed picks up the waterline length actually increases and the long overhangs allowed for this.
Many modern designs have the swept-back transom and this was to decrease weight in the stern, but the other thing, if you look closely, is the underside of the hull slopes up to a point and then the sloped transom begins.
Now then, if the stern of the boat sits so low that the water rolls up the swept back stern you're loosing speed. If your boat resembles this picture then if the weight is moved forward so the stern comes up then the boat can go faster. By the same token, you don't want to burry the bow so it's a balancing act.
An example of this was a Hunter 35.5 that won their class in the Pacific Cup race from San Francisco to Hawaii. They noticed this effect and moved weight forward and boat speed increased, consequently they won their class. Yippee!
A clean bottom and no motor/prop drag was a good recommendation. Going downwind and even on a beam reach the centerboard might be able to be angled or raised to reduce drag.
As for the 250 pounds, yes, it may be more than one person if they are naked but I wouldn't nit-pick it. However, my woman brings "stuff" along. Maybe not the kitchen sink but close! This is not Florida where bikinis rule.
A heat wave into the 90s is forecasted for next week though.