Raw Therapee didn't open DP2 Quattro files for me, but they made 4806x3202 images from DP3 Merrill files which Sigma Pro makes at 4704x3136.
The attached is a Sigma Pro file 67% opaque registered on the Raw Therapee version. The green in the highlights is from the Raw Therapee side. My stumbling around in Raw Therapee produced a non-green version, but the program crashed before I saved it and the redo...