Well now that's 3 of us thinking about doing the same thing
Seems like the lightest battery you could go for would be around 320g (11.2oz). That would be a 5S 2600mAh. So that's about 150g saved off the regulars setups, 450-550g seems to be the norm for 1/8 buggy lipos (4-6S).
The 1509 2Y is 1820 KV so it should be pretty efficient on 5S. The finned can version is 225g so that's another good 100g saved, T8s and 1512 are both around 300g. It's hard to compare for sure cause you never know if that includes wire weight or not.
That means you could easily save 250g (0.5lbs). But 5S means you cant really go for a lighter ESC than the RX8 or MMM
If you keep the light theme going everywhere else in the buggy an under 6.5 rtr weight seems very doable. And maybe such a light weight will make a less punchy 1509 motor perform just fine with a lowish amp draw (allows to run 10-15min on 2600mAh). That's of course on a small track geared for maybe 30mph or less.
Opinions?
the RSpro/R1pro will handel a 5s...
