BRIAN - Back in the day, on full sized tractors with a dual on the land wheel We used to plow 20 acres of old hog pasture every year, normally tough alfalfa sod but some of the ground would be totally smooth & bare but still pulled hard. When the main land wheel starts spinning the sidewalls squat just a bit and the lugs bite deeper into the ground the dual wheel does start increasing it's footprint and helping to pull the load. Plus it's added weight. But there would be places where the dual wheel wasn't leaving any tracks on the ground. This was on a very hard surface, in old corn or bean ground the dual would be in contact just about all the time.
The pull or "Draft" of a plow is directly proportional to the amount of dirt it's rolling over at a constant speed, the 12" Brinley should pull about 20% harder than the 10". One BIG factor is that plow bottoms are only designed to pull efficiently when they are as deep in the ground as one-half their width. So 10" Brinley = 5" deep, 12" Brinley = 6" deep. Once You get a plow socked into the ground as deep as the bottom is wide the pull goes WAY up.
I remember one time DAD wanted to add to His garden and tied a 14" horse-drawn plow to the drawbar of the Super H with a chain to turn over some sod. He got a little deep in some spots and pulled this 5500# 30 HP tractor to a stop trying to pull this one-bottom plow 12-15 inches deep. This tractor should have been able to pull 2-14's in 2nd gear in those conditions at a "Normal" plowing depth but I was spinning out in 1st gear.
I always run about 65-70# of weights on both wheels of the 72 and the best performance I had at a PD I had an extra 50# plus the 65-70# on the land wheel. You can adjust "on-the-go" with body english for difficult traction conditions and tough spots. I also think the smaller normal length CC's transfer weight from the front to the drive wheels much better than the GST's with their longer wheel bases, but You can get them "Light in the front" also.
Depending on if You can run weights "inside" on the rear wheels (internal brake rearend) or not (external wheel-mounted disc brakes) I would think 75#-100# on the furrow wheel and 50# more on the land wheel would be a good combination. Two or three CC weights on the outside of the furrow wheel shouldn't be a problem picking up dirt and raising the tire off the ground, four may be a problem.
One thing I will say, plowing on a CC is fun but it's a WHOLE LOT rougher ride than plowing on a full-size tractor. The more I look at Steve's 782 plowing the more I think I need to make a set of duals! Someday SON & I will have both the 70 & 72 at a plowday. They might even have duals on!