I think the key for ribs is to have a properly operating temperature gauge/thermometer. If the egg gets too hot, you will dry out your ribs.

That said, if you have no platesetter, I would put a drip pan, perhaps an aluminum one that can be discarded, under the grid. It also is a heat barrier for you.

If you have baby back ribs, the 3-1-1 should be about right. It usually takes longer for spares in my experience. But the method is as close to fool-proof as you can get.

Get the temp to 240-275 and go three hours indirect. Then wrap in foil or stand the ribs in a pan with about an inch of apple juice and cover with foil. Cook for an hour.

Then I like to stay indirect for the last hour. The racks or half racks should be flexible when grasped with tongs at the end of the hour. If they are already about to fall off the bone when you remove from foil, then maybe you should shorten this stage. Also, some like to go direct now to cook the sauce onto the ribs, but they are so tender now that you must be careful not to tear them up or burn them.

Saturday night I attended a party where each couple was asked to bring a rack of ribs and an easy side dish. I cooked spares in a method similar to above. My egg settled in a little lower temp-wise than I had hoped (I ran an errand during the first three hour-stage, so I erred on the low-temp side), so I had to cook a bit longer, and it ended up being roughly a 7-hour cook. These were very thick, meaty ribs, and they turned out great, to the delight of our friends at the party.