I would stick with the large breed puppy food. I did however, take Cano aff from it a few months ago, because he was getting fat, and he ate the recommended amount, and was very active. Now we have him and lamb and rice formula, and it works great. Cano is also only 9 1/2 months and weighs 65.5 pounds!! So I don't think he needs to put on more weight. Hid figure is looking like it should.
But being that your dog is only 40 pounds still, I would keep her/ him on for atleast a full year. I know how expensive the large breed puppy stuff is. But it is good for them.
"Every beginning is some other beginning's end" Closing Time- Semisonic