Almost all +4s that raced in the 60s , especially those involved in longer distance events had twin fillers.
It certainly fills a lot faster , and I have never found it exiting from the other filler in road use. After putting in almost 20 gallons (85 litres) I tended to suffer from acute financial shock!
I think almost all early +8s had twin fillers, but I am not sure just how long this was standard or an option.
