I am going to start this by qualifying that I am not claiming to be an expert. These statements are based only on my own experience, observations, and opinions. I welcome yours.
I've seen several opinions over the last several years concerning the importance/unimportance of vehicle weight in Electrathon racing. Some have said that weight only matters while getting up to speed and plays little role after that.
I would point you to the following two videos.
The first is of a race at a "flat" 1/2 oval stock car track.
You'll notice the difference between the wattage usage on the front and back stretches while the speed remains relatively constant. This is due to a slight difference in elevation of one end of the track to the other. Probably about 6-8 feet which over a length of a 1/4 mile is not much of a grade.
The second video is of a 2.3 mile road course with lots of elevation changes which just further demonstrates how elevation eats up power.
https://youtu.be/7c-3L9-qhjg
https://youtu.be/mrHKr6KpAu0
Another thing to consider is that acceleration changes dontd only happen during the beginning of a race. Small (and sometimes large) changes occur frequently as you setup for and then exit corners or while avoiding other traffic.
Some statistics I've read state that the general relationship of weight to efficiency benefit is 2:1. For every 2% of weight reduction there is a 1% increase in efficiency.
I very much agree...
in practice (real world vs theoretical) weight is not as important as a well "rigged" car (ackerman angles, frame "in line" etc.)
unless there are a lot of tight corners which cause you to have to brake hard, or a lot of veritical distance (hills) you just keep an even speed
once you get "up to speed" inertia does the rest....
I weigh 70lbs plus over minimum weight spec. and my car is heavy as well... but I often best drivers who have to use ballast to make min. weight
the secret... rig your car well, use maximum tire pressures, and most of all DRIVE SMOOTHLY (no unnecessary braking or speeding up)
get used to feeling more than 1/4 lateral Gs (a portable G meter I once carried showed over 1/2 g in corners)
often times our cars can perform at much higher levels than we the drivers are comfortable (or capable) of.
this all said don't build a 500lb monster... even a small hill will "suck the amps" and you'll never see the end of the hour...
also it would be dangerous to other drivers in an accident...
but if 1-2 lb will make a stronger, safer car...... don't fear the weight....