Warrior Cardio

Has anyone else here read Martin Rooney's Warrior Cardio?

I've tacked on his "Category 1" hurricane to the end of my upper body training days and follow it up with 30-40 minutes of steady state aerobic work during this cycle focused on metcon.

Cat 1 is originally prescribed as:
9x 15s @ 9mph/10% incline, rest (walk) until HR reaches 120bpm.

I've modified it as follows:
9x 15s @9mph/12%, rest as needed (work:rest ratio usually falls around 1:5-7)

I use the incline as the level of intensity which I can modify during training as my treadmill can only reach 9mph via it's "quickspeed" setting which allows me to change speeds with a single press of a button. Last week I ran at 10% grade, this week is 12%. Next week it will climb to 13 or 13.5%, possibly more, depending on how my calves, achilles (achilli?) are handling the incline.

Any thoughts?