Doesn’t exactly answer your question, but this might help.

My experience is that the Horton kit does very little to improve the M model and newer airfoil. Cessna knew how great the Horton kit was so they changed their airfoil to mimic it very closely with the M model. Yes, you tend to lose a little speed on the older models. We had one on our K model. I absolutely loved it. Horton cuff, fences, and tips along with the 40* flaps make it a great short field plane. I bet you wouldn’t lose much speed, but you won’t gain much performance either. I own 2 N models now and have no plans to install it on either one.

If you have an M or newer, I would consider the Sportsman kit.
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Sprocket Aircraft Management LLC
77 C172N
78 C172N