O/U to SxS gun fit advice needed

[Andy]

I had an O/U gun fitting by Keith Lupton some years ago and had Rich Cole do a Silver Pigeon with semi custom stock to my dimensions as a field gun. It just points dead nuts on. I have had 2 LC Smiths, both too much drop (the 12 FW Elsie is up for sale and I'll post that soon). The only SxS I have now is my 28 repro and it's close to my dimensions and I shoot it pretty well (for me) and I love how it mounts. I am not opposed to a SxS fitting, but time is the issue more than money. I googled and searched this site but can't find an answer to this: is there a way to make a move from O/U to SxS fitting dimensions? I notice on my Parker I see a bit more rib, while on the Beretta I see just bead, no rib (maybe due to slightly more drop?) Granted, my mount is not the most consistent thing in the world but this is my observation. Here is what I got for fitting for O/U followed by what my Parker measures.

O/U Fitting
Cast off 1/8 to 3/8
Drop 1 7/16 at C and 2 1/4 at H
LOP 14 1/4 (single trigger)

My Parker 28
Cast off 1/4
Drop 1 3/8 at C and 2 1/8 at H
LOP 14" (front trigger)

I am just dying to buy another Parker but I won't buy something I can't shoot with or point well. Any advice to give? Or is nobody as anal as me and you just dish out wads of cash for guns and live with the dimensions?