Hello John (aka Insightman),
The swirl of communication regarding weight carrying ability seems overblown. It is true that the number one determinant of fuel economy is weight. That notwithstanding, lets look at the numbers:
It seems from these numbers that:
a. If one buys an Insight without A/C, then one has 31 pounds more person/cargo ability without thought.
b. Keeping the gas tank only half full increases the limit to 365 + 42.5 = 407.5 pounds for Person + Cargo.
c. Even at the limit on every front, with A/C, adding 23 pounds increases the weight of the car by only 1%.
The decrease in fuel economy may or may not be related linearly to the weight. From the MPG numbers being reported in your website's Feedback section, it seems the effect of being a few percent overweight will be in the noise compared to personal driving habits and the trip environment.
A car (the Insight is a car) is a tool. If you put an extra 50 pounds in the car to go visit grandma you are still saving gas. You may be lowering your "personal" MPG by maybe a percent since the gas tank does not stay full (the Insight is a car and consumes fuel).
So don't worry, be happy.
[Bob, you've presented some good points. My personal belief is that the 365-pound weight limit is based on the capacity of the suspension, not the impact on fuel efficiency. To reduce the harsh ride the hard, high-pressure, high-mileage tires might cause, Honda reduced the unsprung weight to what must be the lowest in the industry. They also tuned the springs and shocks to minimize the effects of the tires based on the median weight capacity they designated for the Insight. This median design weight had to take into account the variability of the fuel load, cargo load, person load, and the weight of the A/C. It seems logical that the 365-pound limit would be based on the maximum combination of these weight variables. If the springs are always compressed further than they were designed to be, then the shocks are never allowed to extend fully, thereby concentrating their wear into a narrow region and causing the car to "bottom-out" more easily. It would be great if Honda would offer their comments on the 365-pound weight limit--InsightMan.]