You're already over 1 oz. dryhops per gallon of beer as it is. And when you rack the 5.1 gallons you collected to secondary, some of that will be lost to trub.
HBT Heady Topper clone attempts are continuing to evolve. While the page 1 recipe will create a fine beer, it is not a perfect clone for Heady Topper. It is lacking the appropriate bitterness and/or contains too much caramalt, and the hop profile is not completely nailed. No actual hops are boiled in the real Heady Topper either. Additionally, I'm in favor of a 148-149 F, 90 minute mash and substituting about 4-5% turbinado for base malt to aid dryness. The water profile is also extremely important.
If I were to clone again, I would advise gaining some IBUs during the whirlpool instead of relying on 100% of the isomerization at boil start. Again, no actual hops should be boiled:
1.073/1.074 OG
1.010/1.011 FG
7.5 gallon boil
5.5 gallon batch, collected in primary
12lbs, 84.2% Thomas Fawcett Pearl Malt
12oz, 5.30% Turbinado Sugar
12oz, 5.30% Thomas Fawcett Wheat
12oz, 5.30% Thomas Fawcett Caramalt
14 ml HopShot @ 90 Minutes
2.50 oz. Simcoe pellets @ 180 F Whirlpool
1.00 oz. Centennial pellets @ 180 F Whirlpool
0.75 oz. Columbus pellets @ 180 F Whirlpool
0.75 oz. Comet pellets @ 180 F Whirlpool
0.75 oz. Apollo pellets @ 180 F Whirlpool
1.50 oz. Simcoe pellets @ 8 day, Two-Stage Dry Hop
1.50 oz. Centennial pellets @ 8 day, Two-Stage Dry Hop
1.00 oz. Columbus pellets @ 8 day, Two-Stage Dry Hop
1.00 oz. Comet pellets @ 8 day, Two-Stage Dry Hop
0.75 oz. Apollo pellets @ 8 day, Two-Stage Dry Hop
Conan @ 63 F, then after ferm slows down drastically or completes, rack to secondary and ramp up to 68-70 F. Be wary of ambient temperatures. You don't want the wort in the primary going over say 64 F for the first week.
^The majority of these hops are very piney, dank(marijuana), and full of pungent grapefruit. Centennial is really the only somewhat fruity hop. I am open to minor tweaks if you guys attempt this beer and are familiar with what these hops bring to the table.