ADBA is very different from UKC. For untitled dogs, your class is broken down not just by weight, but by gender. Ellie, assuming Maya still weighs 50#, she would pull in the 46-55 female class. She would compete for overall percentage w/all the dogs 30-55# (ADBA won't calculate a dog's weight under 30#, so Soleil at 30# competes in the 35# and under female class). The ADBA runs 3 main groups that compete for 3 trophies, the Aces (accrued a 100 points), the 55 and unders, and the over 55#'s.
In ADBA class dogs accrue points differently than aces, except at nationals when all males pull together, and all females pull together and points are different too. In the regular classes, you earn 8 points for first in your class, 5 for 2nd, 3 for third. Winning overall percent for your group(such as 55# and under) is an additional 15 (I think) points. There are no points for most weight pulled. I think the dogs are all grouped together if the are over 75#, which makes it hard to get points if you have a huge dog, because everything's based on %. The disadvantadges to very large dogs, and dogs under 30#, is an attempt by ADBA to get rid of people crossing in other breeds and hanging papers.
You can come in at any weight increment. They do vary the weight increment sort of like APA. You can ask for "body shot" if you are getting near the end of what your dog can do, and you are the lightest dog still pulling. So when Soleil was slowing down, and was the lightest dog pulling, I asked that they go from adding 200# to 100#, trying to get the highest percentage. Once she dropped out, the next lightest dog can do the same.
So, if you were the only dog in the 46-55# female class, and Maya only pulled the empty cart, she would still earn 8 points. It's just harder to earn an Ace title than a UWPCH because there are a lot less pulls, and the competition can be pretty stiff.