Buck,

Its hard to really give a definitive answer to questions like this, aside from personal experiences on my motor and the one's I've serviced. The consumption numbers on the PST site are a little on the conservative side, meaning there should be extra left over if you base your flight time estimates on the official specs.

I fly my stingray largely at the same throttle setting you expect to run. The tanks are suppose to be ~75oz, but some say that's a little optimistic so lets say 72oz. (I'd confirm, but the Jet Tech site appears to be down at the moment) I don't fly with a startup tank either, so the startup, taxi time, etc all comes off my main tanks. I fly for ~7 min and land with the 2nd tank ~1/3 to 1/2 full depending on how far I put my foot in it.

Kelly