I'm certain you're correct, Bob, a taller screen would add efficiency. I cut it as you see it so it would nest inside the pot, under the pot's strainer. It's maximum height under that constraint. As is, I'm not complaining about efficiency, the 30 hole SuperCat is giving me 4-min boils for two cups of water on 3/4 oz alcohol, with flameout at 6 min. Part of the reason is the Grease Pot's wide circumference...the flame must dwell along the bottom of the pot a long time before going up the sides.* Other stoves can do better, efficiency wise, but I'm not complaining. I AM complaining about flame stability in wind, and keeping it lit.
One other possibility I'm considering is making myself a "SimmerCat," same stove with only one (top) row of holes. Such a stove would need less air, allowing a tighter windscreen around the circumference. Also the vertical distance between the holes of the windscreen and the holes of the stove would be greater. And, on top of that, I've been reading that slower stoves are generally more efficient. So maybe I need to make myself a new cat stove to get a more stable and dependable flame.
*Off topic, one "problem" of the grease pot, IMO, is that it's too tall, with too much capacity for solo. It's 4-1/2 cups. It would be nice to be able to re-roll the lip of a grease pot about an inch lower, to get a squat, wide pot. Can't beat the weight, though. These grease pots are lighter (and more conductive) than Ti. (Not to mention, $7 at Kmart).