I believe the mystery hop we are all missing is Comet. There is likely no Amarillo in Heady Topper.
It has also been stated several times that Kimmich does not boil any hops for Heady Topper. He relies on HopShot for nearly, if not 100% of the IBUs in this beer. So, instead of a hefty 8.50 oz. mixed hops at 5 minutes and 0 minutes, it is likely that Kimmich uses slightly more HopShot, and implements a warm hopstand around 165 F for all of the hopstand hops instead. This temp. is below the 167F myrcene boiloff threshold. Myrcene is that hop compound that offers floral/citrusy/pine.
Lastly, I've never seen a commercial clone or brewed an IIPA whereupon the recipe called for more hopstand hops than dryhops. The dryhop regimen always contains the largest amount of total recipe hops by weight. Pliny, Double Jack, Head Hunter, Tricerahops, Kern Citra, and Alpine all go by this idealogy.
For that reason, I think there is likely 6 to 7 oz. dryhops per 5 gallons beer and only 5 to 6 oz. total hopstand hops per 5 gallon batch.
1.074 / 1.011
86.9% Pearl Malt
4.60% Corn Sugar or Turbinado
4.60% White Wheat
3.90% Caramalt
13-14 ml HopShot @ 90 Minutes (shoot for about 155-170 IBUs)
2.50 oz. Simcoe @ 160 F, 45 Minute Hopstand
1.00 oz. Centennial @ 160 F, 45 Minute Hopstand
0.75 oz. Columbus @ 160 F, 45 Minute Hopstand
0.75 oz. Comet @ 160 F, 45 Minute Hopstand
1.50 oz. Simcoe @ 8 day, Two-Stage Dry Hop
1.50 oz. Centennial @ 8 day, Two-Stage Dry Hop
1.50 oz. Columbus @ 8 day, Two-Stage Dry Hop
1.50 oz. Comet @ 8 day, Two-Stage Dry Hop
0.50 oz. Apollo @ 8 day, Two-Stage Dry Hop
Conan @ 63 F, then ramp up to 68-70 F after ferm slows down/completes.