Ted, t o your Post#17 -
1) Glen Allison, down here in Tucson, did a profile that had a stabilator, hinged about 50% MAC on one of his orig profiles. The model was IIR unflapped. He controlled the "aft of MAC" tendencies with, in effect, an anti-servo tab. He and Keith T had an interesting discussion at a Cholla Choppers meeting about the exact nomenclature and function of the TE counter-tab. It did work, though... Glen had an article on it in the same SN issue with Drindak's 80% hinged stabilator model... Short, ~ 1 pg articles...
2) I also dabbled with them for a while, and found pretty much what's been aired in this thread. Restated, a bit closer to my observations, stabilators can have enormous turning power. That includes a risk of "locking-over" too far, and not being easy to bring back to neutral. I 'd also been flying some RC soaring about that time, and many of those models used 25%-hinged stabilators.
Figuring I did not want to lock one over, and that LE-hinged layout might require to much muscle, I designed the hinge at 20% MAC. That, at least, worked reasonably well.
Then there's an idea that such a layout does not need the vast horizontal tail area of fixed-stab/moving-elevator designs. Also true.
As was an idea you and I may have been known to mention over lo, these many years. (Well, you maybe - who listens to me?
) The idea that a stabilator is pretty much a symmetrical airfoil control surface, while the stab+elevator forms a crude, cambered-airfoil surface. Also true.
That suggests the stabilator doesn't need as much angle to get similar control force. ...that perhaps an angle comparable to the "chord line" (LE to TE straight chord line) for a deflected stab+elev is adequate. Also true, and in spades - the symmetrical section doesn't have the awkward bend in the middle that compromises 'streamlining' and adds drag...
Now, before anyone runs out and tries it on the basis of all these positive ideas, there were some negatives, too.
STATIC balance for the stabilator was important. If the surface static balanced aft of the hingline, the model tended to gallop. (The terms "up" and "down" I'll use refer to the direction of required lift, not ground and sky, ok?) In level flight, and aft-heavy stabilator tends to trail at a slight positive AoA, meaning a "down elevator" tendency. With the 'prongs' of the joiner wire bent forward, and perhaps another touch or two of ballast to make sure the surface static balanced just ahead of the hinge, the 'free-trailing' tendency was slightly nose-up. Since level flight requires a positive AoA - however slight - it didn't cause the same divergence tendency as an aft-heavy stabi.
Grooving? Tracking? No, VERY unlikely. You fly the beast every inch of the way... That didn't affect RC soarers, since the servo pushrods are a 'dead hand' in effect. Where you move the stick to is where the servo wheel stops, and thus also the control surface. With our immediate, direct, free, feedback in CL it don't woik that way at all. Generally, it wasn't too bad, about like solo-sailing a small sailboat in choppy and gusty waters... A challenge, but (almost) physically enjoyable...
And, finally - ultimate control/stability power. Ain't got it... That big fat stabilizer in front of that big fat elevator on modern stunter layouts do got it... Plenty of elevator to start and execute a sharp turn, and plenty of stabilizer to stop it. On my 5 or 6 experimentals I learned that oversize stabilators were more nuisance - excess control force, poor exit damping, balance, etc... So, a stabilizer proportioned for fully adequate control in soft conditions ran out of muscle in nasty weather. Particularly at places like the bottom turn of the hourglass. Guess how I found out...