Originally Posted by
barturtle
Foot over toptube, in front of seat. I have to do this when I have my rear mounted waterbottles in place for long-distance rides.
Likewise, just step over ahead of the seat. That's how I take my welding cylinders to be filled -- I don't own a truck, and for safety/liability they won't fill acetylene cylinders if you're carrying them enclosed in a car.