Its strange as I didn't think about a body as a setup item until I had a consistent car under me, but I find there are a few tips and tricks that can make a difference with light weight shells.
I usually have 2 shells with me, one setup in a normal position and one setup forward. With the one setup forward I can get a little extra steering when the track is right and grippy. I also put an extra strip of thick but still squishy foam between the bumper and the bodyshell.
On my Yokomo the body touched the front shock tower this helps a little as well.
The other thing I like is the threaded adjustable body mounts, so you can get the body at the exact height all the time, and I also don't have the body pins hard up against the shell to give it some flex along with the car.
Because I hate painting body shells, I also put a small layer or shoe goo and a layer of fibre tape reinforcement at the very front and rear side to stop when getting tapped from the side and body getting stuck.
last trick, don't use the wing that comes with the lightweight shell, the Yokomo 4.0 wings are really good for a non full carbon fibre option.