Mixing foods and staying mixed?

Seven is on Innova Adult Dry currently. He was on Solid Gold Barking at the Moon previous, too much protein I think (42%), soft stools. Anyway, I wanted to give him more protein than 24% because he gets a lot of exercise. I just got him Innova Evo which has 42%. Mixing the two will give him 33% protein. Is it ok to keep him on the 50/50 mix if his stools look ok? Thanks.