Fuel pipe diameter

[Steve Bryant]

I'm currently sorting out the items required to make up the fuel line from the shut off tap to the Bronze Zenith Carb on my AD type seven.  I need to order the copper fuel tubing for this.

So... is the tubing 5/16" or 1/4" diameter?  I'm thinking 5/16 but would like to get confirmation on this.  Would three feet be sufficient to include the vibration loop or should I get four feet?

Thanks for indulging all these basic questions.
Cheers,
Stephen