Canadian drags are ACCELERATING uphill.
You still dont get it, when you drag the engine down in rpm dyno has to brake all the rotating mass from engine, transmission, tyres and even its own rollers. That gives false readings, Doodle proved it. It doesnt matter overdrive, direct or underdrive, higher speed just gives higher horsepower.
Steadystate is ok for stock engines that dont melt itselves, but for heavily tuned engines acceleration is safer, it just gives little bit lower numbers. Controlled acceleration with dyno controlling acceleration rate, not free rolling inertia dyno.
We didnt found pull down mode from US made Mustang dyno software, maybe they dont know what they are doing ?