The rub is that the reg allows proficiency to be demonstrated in an aircraft 'or similar make and model of aircraft to be flown". And the 'maneuvers and procedures... appropriate to the make and model of aircraft to be flown' could be accomplished in any light fixed-wing aircraft. Not an approach I'd take, personally, especially with an initial solo; I want to see the student fly that particular make and model aircraft by observing from the seat right next to him before I sign him off One of many cases where the regs spell out only a minimum standard which most of us strive to exceed...

There are some provisions for pilot examiners to observe some maneuvers from the ground, but I have yet to meet one who would sign off for a rating based on ground observation.

If I'm not mistaken, an RV8 is too heavy to apply to what I'm referring to. There are a lot of lightweight kitplanes flown by owners who have had little more than a couple of lessons -- I've met a couple of them myself I gave instruction to a guy who had been flying his own kitplane for a few years, unlicensed, unendorsed for solo, just a guy who figured if he built it, he could fly it, and indeed he could, and did He thought he was exempt from the pilot certification requirements due to his aircraft being an ultralight, but as it turns out, although it was light enough, it had two seats, which changed how the FAA looked at it. We spent some hours in his aircraft, got him signed off for his solo flights and solo cross-countries to build up his 'legal time', and because we couldn't find an examiner who would go up in his airplane with him, we transitioned him into a Cessna 150 just for the purpose of taking the checkride. He hated that 150, said it was too big!