I'm posting this here for my own reference and for anyone else who may be looking for it:

"K Factor" for tailplanes.

K= (Stab Area)x(distance between 1/4 chord points) divided by (Wing Area)x(Average wing chord)

Really nice flying planes have K~0.5
Trainers have K~0.6
Racers and high aspect ratio sailplanes K~0.4
K~0.3 is almost unflyable.