Some months ago I too came up with low 200s for horsepower. I have a recollection of using a different method to you. It's notable that those of us here who can calculate this sort of stuff, are all getting similar numbers to each other, yet wildly different to Peter's ever rising hp.I did calcs on hp based on the acceleration and static thrust tests months months ago and came up with around 225-250- far short of his 400ish hp estimates.
The gear leg attachments look mighty flexible to me and that prop got pretty close to the ground there from the video.
One question for my US friends here, can someone qualify for insurance without a minimum number of flight hours in the previous year? I've never seen Peter mention anything about flying to stay current though I might have missed it.
Bill Clapp was giving him some test pilot lessons in his aircraft. Peter has at least a few recent hours.
When he first moved to Valdosta, he was talking about maybe getting the resident test pilot to test it out. I guess Bill Clapp declined that.