I used these.

The English 5/16" worked well as that was the only one I could get!

These will fit in the tight space on the line next to the bulkhead. Anything longer or bulkier will not.

There are plastic models out there as well and they will do quite fine as you only use these once or twice.

http://www.harborfreight.com/automotive-...tool-97576.html

http://www.harborfreight.com/4-piece-a-c-fuel-line-disconnect-set-98118.html

What's your mileage? Who cares. Is it practical? See #1. What happens when it rains? You get wet.