Agree with Lew. In addition, another thought. If you are diligent about closing all vents after you are done your cook you really don't need to worry about how much fuel to put in the ring.
Here's why. You put the fire out when you are done cooking. Next day you shake things out and put the unburned fuel in a container and set aside for the next cook. You use the unburnt fuel, you don't just toss everything.
A few minutes extra step is all. I use lump exclusively for years, but I have found that this works just as well with briquettes.
So - I always load the ring to full. I minion start unless I want a really hot fire and fast ramp to high temps, say when I'm doing a roadside chicken cook or the like on the WSM.
Load the ring up, minion the start. When the cook is done close all the vents and walk away. Next morning pull/shake out the unburnt fuel and save it for the next cook. Makes things simple, and you won't run out of fuel. Well maybe on a really slow low but you can check and add coals from the side door if you need to.