The proof of anything is always in the using... well, in using my rainwater barrels for watering I have found that because of the height of the barrels, I was wasting too much water in spillage whenever I filled my watering can.
Lowering the barrels was not an option because I need the difference in height to make the overflows from one barrel to the next really work. So I figured that adding an extension hose to effectively deliver the water directly into the watering can was the way to go!I got some old garden hose and bought some fittings for about a buck each and custom made hose extensions for each of the higher barrels. Each extension is incrementally shorter as the barrels go downhill. The watering can fits under the hose and it keeps all the water in the can... No spillage. Problem solved.
Necessity is the mother of invention!