The Mamiya 127mm f3.8 lens covers 4x5.

I just tried it on my Tachihara 45GF. Coverage is tight with no movements practicable. Incidentally the 155mm X 192mm "area covered" specification for the 127mm lens refers to the amount of subject the lens sees at its closest focussing position. The bellows focussing on the Mamiya RB67 makes all lenses "macro" lenses; a very nice feature.