In Peter K's answer to this elliptical wing with lowest drag question the minimum induced drag lift distribution for a wing is described as one with a constant downwash angle across its span. When a forward lifting surface is involved, as with a three surface aircraft, it creates its own downwash across its span and upwash beyond the tips. Both impinge on the larger main wing.
Is the combined minimum induced drag for both lifting surfaces still one where the main wing downwash angle is constant across its span?