you are right 600A is a stretch of the imagination. but the 10C multistars 150A rating is not as unrealistic.
but what it says on the box is what we have to go by. we can only ASSUME that the company isnt lying to us.
I can’t talk for your 600A lipos, but the multistars in my mates board has been hawling him around for years, and one time when we forgot a remote his board pulled BOTH of us. thats around 380lbs. I would have liked to see the current draw on that day.
Yeah unfortunately ammeters always include some bulky component (either a shunt or a loop) and I keep breaking them… think I’m going to have to hook up a bluetooth module and get metr working.
I should have the equivalent of 75c and 15A when i’m finished, which means a constant current draw of 1125 amps 
Voltage sag isn’t a problem I need to worry about, even if Zippy is drastically exaggerating their C ratings.
Hoping to do some testing with the new set up over the weekend, just finished soldering the new cables together.
I’m also designing some modular battery enclosures, which I’m now thinking about incorporating some fire retardant fabric on the inside…