fnp,

You can use the TLAR (That looks about right) method it works pretty good.

Another method is:

Horizontal Tail:

Pht=Dh/MAC * Sht/Sw >= .55

Pht horizontal tail power, empirical value
Dh distance from the center of gravity to .3 chord horizontal tail, ft
MAC wing mean aerodynamic chord (or average wing chord), ft
Sht total hrizontal tail area, sq ft
Sw total wing area, sq ft

Vertical Tail:

Pvt = Dv/MAC * Svt/Sw >= .3

Pvt vertical tail power, empirical value
Dv distance from center of gravity to .3 chord vertical tail, ft
MAC wing mean aerodynamic chord (or average wing chord), ft
Svt total vertical tail area, sq ft
Sw total wing area, sq ft

Steve