Maybe use a right elbow our of the 3-way valve to go further right, then a couple left elbows (u-turn) further away to give you move length in the back run? Or you can use their vertical installation kit?
I think you're spot on. I think that will make for an easier install and save me a mile of PVC.Mine is now vertically oriented. Used to be horizontal until a pad re-plumb. You may save some footprint area by doing that.