Colmbo - the difference aerodynamically speaking closely approaches zero - if anything the slightly reduced surface area of the B is to the advantage of the B. The ONLY difference in the wing is the slighlty elongated root chord of the D to accomodate the new wheel well/wheel door modification by giving that inboard section a more pronounced 'strake angle' from WS 17.5 to WS 61.5 on the D.
Having said that, there is no difference between the A and the K in area, incidence, twist, thickness ratio, span, dihedral, taper ratio, mean chord length, washout, camber, area, aspect ratio, MAC, airfoil section incidence at the root. Only the H (of production models) had changes to the above data.
Having said all of this relative to physical data - the models to not account for ANY of the above (nor should they) and focus on CLmax (of power on level flight stall), Weight, Aspect Ratio, and HP (at the recorded altitude and speed) to develop Drag - and even with that I wonder if in the case of Merlin P-51s whether the modellers consider the compressibility effects for high altitude/high speed? (Ditto for Me 109K and Spit XVI, etc) - last - does anybody know if exhaust thrust is applied as it ranges from ~ 11-14% 'depending'.