I would also note that the associated 25-sized airplane, The Medic, is the same thing, scaled down. Think of it like a Super Skyray. To be honest, when we got Bob Hazle's old Medic trimmed (after he sold it to Paulette Erickson AKA Mrs Uncle Jimby), I thought it flew better than the prototype Doctor in most conditions, just because it was enough "denser" that it wasn't so prone to getting bounced around in turbulence.
Both airplanes are are *extremely* easy to trim and fly, as intended, with the fingertip control forces. The published plans for the Doctor, I think, are smaller than the original (which was bordering on huge) to try to reduce some of this effect. You never have any real problem in *any* reasonable wind, but the big one sometimes requires huge compensation angles, like flying a kite.
The other thing is that these sort of airplanes illustrate how much engines have improved to a much greater degree than flapped airplanes. The sensitivity of the controls varies strongly with speed, the faster, the more sensitive, which if anything is the opposite of flapped airplanes. This puts a premium on tight speed control and will very quickly show you how much more 4-2 break systems (even good ones) change speed in flight than modern systems running 4" of pitch. Put a 50's stunt engine, even working perfectly as intended, on the Skyray, and it flies like a typical "trainer" from the 50's/60's/70's, i.e. like crap. I could get it through a pattern in a moderate wind, but it took expert-level skill to make it merely recognizable, with a lot of practice. 20FP, it's like falling off a log in any wind you would fly in, and I will pick it up after a few years and fly a 500-point pattern on the first flight.
Both airplanes are highly recommended, and I had forgotten how much Ted and my lectures on the topic of these simple airplanes overlapped. The interesting thing is, I don't recall who did what first! Probably Ted and I just parroted him (since I am just his "mindless puppet", to quote a famous PAMPA politician).
Brett