Move the sun, turn the wall, stretch the overhang and the fins — and watch MEEB Fig. 8.28's two formulas recompute in front of you. Every number on the right is the shading calculation, worked live on the inputs on the left.
Three things the sliders make obvious that the formulas alone do not.
The sun off to the side casts a steeper shadow down the wall than it is high — cos HSA in the denominator. At HSA = 0 the two are equal; at HSA = 60° the tangent doubles. That is why an overhang sized for noon still shades at 3 PM.
ALT 26°, HSA about 9°, VSA about 27° — a 6 ft window needs a 12 ft overhang. Now give the fins a projection and watch the plan: at low HSA the fins do almost nothing either. MEEB's answer for east and west is not a device; it is do not put the glass there, and if you must, fins on a low sun beat an overhang on a high one.
The sun's position on May 21 is its position on July 21; April 21 is August 21. So a fixed device gives the spring the shade it gives late summer. In Detroit April wants the sun and August does not — MEEB §8.6(d)'s reason to compromise at 50% shading, or to make the device operable.
It is one wall, one window, one moment, with a device that runs the full width (overhang) or full height (fins) of the glass — MEEB's infinite-element assumption, truncated only at the window edges. It does not see your neighbors, your trees, or your terrain. Those are what the nine shadow images are for. Use this to size and to check the arithmetic; use the model to see the site.
Declination δ = 23.45° · sin(360 · (284 + n) / 365) for day-of-year n. Altitude from sin ALT = sin φ sin δ + cos φ cos δ cos h, with hour angle h = 15° × (solar time − 12). Azimuth from south by the standard cosine relation, west positive. Then HSA = AZsun − AZwall and tan VSA = tan ALT ÷ cos HSA (MEEB Fig. 8.28). Overhang shadow depth down the glass = D · tan VSA; required depth for full shade D = H ÷ tan VSA (Fig. 8.32). Fin shadow across the glass = P · tan |HSA|; required projection for full shade P = W ÷ tan |HSA|. The combined figure treats the two shadows as independent, which is how an eggcrate behaves. Solar time throughout — convert from clock time with the equation of time and your longitude offset from the time-zone meridian.