Beebe, I agree that smaller cows are more profitable per acre. The smaller the cow the better in those terms, and sheep are even more profitable per acre.
However different environments, body composition, time of weighing, BCS, feed the cattle are on all affect body weight. A 4 frame cow here was not 1250 lbs when we weighed, but they had 3 months to fatten up post weaning prior to the winter. If I weighed them at weaning they would have been much lighter, but once adjusted for BCS they would have basically been the same weight I reported because those were adjusted for BCS - so a 4 frame mature cow here would be in the 1350-1400 lb range with reasonable body condition. Unless your cows are smaller they would likely be the same - unless they are finer made and lacking capacity which I doubt by the pictures I have seen of your cattle.
And also those smaller cows are only more profitable if the calves are selling like the bigger calves. As I said some of the calves from those smaller bulls were coming out a bit stubby and were docked at the sale barn - so the advantage is lost. Also our environment is tougher on those light calves if having to feed through the winter so I prefer to have them at a weight where I can just market them in the fall. Lastly in Western Canada light calves have been selling at a substantial discount to heavier calves in the last two years - especially in the last year due to drought and feed shortages.
So general rules are great and are a good guideline, but a person also has adjust to what is actually happening.