The weather will help a lot. Just make sure to remove a little ballast from the car, and that will help more.
That is a pretty good 60ft you had the last time. I imagine that if you can keep that up or do slightly better, you should have a high 16 on a much cooler night.
The weight from the gas might be an issue, but like I said remove ballast...spare, jack, passenger seat...that should offset the gas pretty easily.
2005 Focus Zx3 se D20 M5 - "Helios" - blazing copper
intake, header, exhaust, xcal2 tune, !CMC, cams, suspension, nitrous, torsen, spec lw flywheel and stg1 clutch
home brew turbo in the works