Too much new Growth in the wrong spot?

Well they are and they are not. With a wide canopy like yours, it is going to fill out the middle. Just select tiny branches from the underside for pruning if you really want them out. But since you are growing outdoor, and doing fine with it, I would leave them to grow fuller and when close to flowering, make a final selection based on sundirection (so branches to the north). I ve had good results outdoor, by pushing the plant 45 degrees towards north, which creates a canopy like bush facing south, your setup is ideal when growlights are directly above. You will still have great results, I think the middle ranches will give you more than the branches towards north! Good luck and hope for a warm summer!