Thanks for the replies, guys.

Since this will be far from WOT, it seems safe to assume 15-30min endurance on a 16oz tank. This project is for an autonomous UAV, and if more endurance should be needed, the fuel tank may always be replaced by a slightly larger one.

Pilotpete2 - Auto fuel in Brazil has a high ethanol content - it has recently been reduced to 20%, from the earlier 25% mix. I'd rather use straight gasoline, but it just isn't available here. We don't have Coleman fuel, either, so I'm pretty much stuck with this 20% mix (or use AVGAS). I have extracted ethanol from auto fuel in the past, and don't want to go through the process again.

I'll keep the forum posted with my progress with this.