Thanks all for the suggestions.
The speed that I usually use is 240% of anaerobic threshold speed.
I did my AnT test on flat ground, so not really sure what the equivalent would be at 15% incline. On flat ground it was ~6:25 pace.
I can’t tell if mine has a speed limiter or not, but it didn’t feel like I was sprinting, nor generating all that much power—despite pretty high speeds.
I’ll give it another shot, however, I’m wondering, if it doesn’t work super well for me, would it be better to just go back to doing the Functional Runner strength routine instead of this? If the idea is strength training, will it matter all that much which one I do?