Dick, my textbook is of limited help. Not very educated guesses:

Lift ratio biplane/monoplane in this case 0.86 (86%). Useful for equivalent wing area.
"Biplane Coefficient" in this case 0.57, hence correction factor for induced drag/AoA 0.79 (coarse) compared to monoplane of same span.

Mean span is (29+21)/2 = 25 m, chord is 2.46 m (ailerons neglected).
Wing area is (29+21)*2.46 = 123 sqm. Ailerons +5.5 sqm makes it 129 sqm.
Effective wing area (0.86) is 105/111 sqm.

Stab area 10*3.6 = 36 sqm.
Ratio is 0.28 (real area) / 0.33 (effective) including ailerons (0.29 / 0.34 w/o).


Wing airfoil has 6.4% camber.
Estimate for zero-lift AoA: -6.4°
Estimate for pitching moment coefficient Cmo: -0,16 (Wow!)

Simple equation for equivalent moment coefficient: Cmm = Cmb (Chordb/Chordm) biplane/monoplane

Equivalent monoplane wing:
mean span 25 m ==> 105 sqm / 25 m = 4.2 m chord (that produces the same lift)
aspect ratio should be bigger by correction factor for same induced AoA and downwash:
AR(1) = 25/4.2 = 5.95 | AR(2) = 5.95/0.79 = 7.58
span = sqrt(7.58*105) = 28.2 m | chord = 105/28,2 = 3.73 m
Cmo = -0.16*(2.46/3.73) = -0.106


That'll suffice for NP calculation.
I'll put it into my monoplane calculator - tomorrow.