I installed one on my old '14 over the Spring. It feels 100x worse than it is. Measure twice and drill your holes with care. The Roush template is good but I ended up also measuring and marking without it, centering each side of scoop from edge of hood. Mark your work with masking tape when doing this. Good luck, you'll do fine!
2016 Mustang Ecoboost Premium, Performance Package: Roush Quarter Window Scoops; Roush Jackal Rear Spoiler; Modded GT Wire Mesh Grilles; Eibach Pro-Kit Springs; Mishimoto Oil Separator; MAPerformance CAI; Drilled and Slotted Brake Rotors; BAMA 93R Tune