My screens are two rectangles with a small lip forming an L . These rest nicely against the two open sides, no vents as the bottom has enough draft. They also fit neatly inside the stove for carry. With a small unit thermal efficiency is everything. People have cobbled all manner of screens. This works for me. My Zebra is substantial steel guage for it's size, so the simmering is helped by heat retention much like a dutch oven. Alcohol stoves et al are fun. Whatever you choose, remember the concept, like a PSK is to have something on you. The ESBIT works for me.