There were some guys on Shotgunworld who created some 3/4 oz and 11/16 oz loads for the 20 Gauge using Promo. They had them pressure tested too.

Here they are:

20 GAUGE LITE
Hull: AA-HS or any Remington
Shot: 3/4 or 11/16 oz. (Stock MEC charge bars. Actual average dropped: 3/4 oz. - 315 gr.; 11/16 oz. - 300 gr.)
Powder: 12.5 gr. Alliant Promo (or 15 gr. Unique or Universal. You'd have to determine which MEC bushing drops that.)
MEC Powder Bushing for Promo: No. 21
Primer: Fiocchi 616 (209), W209 or STS209, Rio, Nobel Sport
Wad: Current "new" WAA20 (The older WAA20 wad and others won't crimp well.)
~
Average Velocity: 1232
High Velocity: 1242
Low Velocity: 1227
Extreme Spread: 15
Standard Deviation: 4.9
Pressure: About 9,500 psi using Promo (Tested). Less than 11,000 psi using Unique.
NOTE: This unpublished load using Promo was cooked up by some of us here on SGW. Burns cleaner than any load I've ever used in any shotgun, no matter what gauge/bore. May or may not cycle semiautos.