DD - You didn't say why you are wanting the 1 1/4-ounce load, but I'm guessing upland birds. If so, I would recommend you use 20/28 or Unique in the 1 1/4-ounce load. You may have to change your wad from the SP12 with those powders though. If you really want to use Green Dot, drop to 1 1/8-ounce loads and you'll find many options.
Here are a few of my pattern numbers from a 1 1/8-ounce Green Dot load and a 1 1/4-ounce Unique load that I've shot many birds with over the years.
Patterning results from a 12-gauge Browning Citori with 28" Invector-plus barrels using Briley flush chokes (patterns average of five, 30" post-shot scribed circle, yardage taped muzzle to target, and in-shell pellet count average of five).
12 GA 2 3/4" RELOAD (STS, R209, Green Dot, CB1118-12)
1 1/8 oz #6 lead (267 pellets) @ 1225 fps
30 YARDS / SK / pattern 171 (64%)
30 YARDS / IC / pattern 211 (79%)
40 YARDS / M / pattern 182 (68%)
40 YARDS / IM / pattern 195 (73%)
12 GA 2 3/4" RELOAD (WAACF, W209, Unique, CB1114-12)
1 1/4 oz #5 lead (210 pellets) @ 1220 fps
30 YARDS / SK / pattern 145 (69%)
30 YARDS / IC / pattern 177 (84%)
40 YARDS / M / pattern 155 (74%)
40 YARDS / IM / pattern 174 (83%)
50 YARDS / IM / pattern 125 (60%)
Good luck!