From what I recall reading, it's just to make sure that you register the battery correctly and that all of the lightweight battery options are less than the lowest setting in the registration setup.
That being said, HPA makes a lightweight tray for Braille and they advertise saving 30lbs with the 21lb Braille battery and their tray. For $440, not bad.
https://www.hpashop.com/HPA-Battery-...-and-mount.htm
The Antigravity batteries are really interesting, but so expensive they're kinda out of the running for me.
I'll follow along, I'm thinking of doing one for next autocross season... It's easier for the car to lose 30lbs than it is for me!!