Now large breed senior was one of the only foods I have tried for my senior Dogo that he could eat enough to be full and loose weight. It is pricey though and right now I am trying Victor Ocean Blend which is working pretty well. Similar guarenteed analysis to the Now.
But if I could afford it I would feed the Now.
Casper gained weight very easily on Acana and Orijen.
Nutrisource grain free large breed lamb was another decent food I have fed. I find the large breeds tend to have less kcal/cup. I feed them to my JRT too.