I've got a Turnigy Ultimate 7500 battery that weighs a little over 310 grams. It performs well but I'm looking for something a bit lighter, in the sub 250g range, as my ancient chassis are already overweight and unbalanced. It seems the lower capacity Turnigy batteries don't really save much weight, they're still around 290-300g. What popular options are out there that don't sacrifice much? I'll be running it in either a 21.5 or 17.5 blinky class.

Look into the Team Powers batteries.

Are you referring to the 5800mAh one? At around ~258g that looks pretty close to what I'm after. Any idea how it compares voltage wise to the LRP LCG range?

Yes. I believe Team Powers states the weights on their website. I have an old 5800mah. I think they have 6000's too. No complaints about the battery.

The HobbyStar standard 90C shorties are 210g, the Lite's for stock racing are 150g:

https://www.rcjuice.com/lipo-batteri...o-battery.html

https://www.rcjuice.com/lipo-batteri...o-battery.html