I must admit, there is a lot being spouted about fuel-line and clips on internet forums at the moment.....heres a quick 101 on what you need to know...
The R9 grade of fuel line has only 20% of the permiativity to alcohols/ethanols of R7 grade - its designed to be compatible with modern fuels that have elevated bio-fuel content.
In short it does not rot quite as fast as older specs of fuel line - these older grades struggle with modern fuels due to bio-ethanol being added now.
Better yet is marine grade - this is fire resistant for two-and-a-half minutes. Its permiativity is 5% of R7 grade. Not available in the correct 5.5mm ID for VWs unless someone buys a Km of it.!!
It can be found in 6mm and 8mm bores if you have after-market carbs etc.
You need 5.5 or 5.6mm inner diamter hose for stock VW engines with Solex Carbs. 5/16 and 6mm hose is too loose a fit. You need it to stretch elastically over the metal pipes to help stick it securly in place. The clip provides a back-up safety force to grip it into place.
Remember : you often get what you pay for with these things..... buy cheap and you will get cheap quality.
With jubilee (worm /band) clips / clamps there is a man-down-the-pub myth that they are no good for fuel hose. They are perfectly good in so far as you have to select a clip designed to fit the diameter of hose being installed. 9.5mm-12mm clips will do the job on a VW.
Fuel injection (norma style captive nut and screw- as mentioned earlier) clips are equally good : again you have to select a clip designed to fit the diamter of hose you are using. #12 clips should work here : but check the fit and clamping effect as sometimes you need to go a size up or down.
Select the wrong size clip in either case and you may as well not have bothered using one at all. I have clamping force diagrams from manufacturers to support these points of view : I can and post them if necessary
Hope this all sounds helpful