Bellows compensation is pretty straightforward. For whatever lens you're using, no compensation is required when the lens is focused at infinity. At life size magnification (1:1), the bellows is extended 2x the focal length, and requires 2 stops. At 1/2 life size, the bellows is 1.5x the focal length at infinity, and requires 1 stop. From there you can calculate your intermediate compensation factors. Below 1/4 life size (a half-stop) unless you're shooting chromes, I wouldn't worry about exposure compensation, because you can't set less than a half-stop on the shutter speed anyway. With the Mamiya C2xx/3xx lenses, I don't know if the fstops are marked in less than 1/2 stop increments, but they're small enough it would be hard to precisely set a quarter-stop increment.