Ok - thanks for the advice group. I will definitely invest in a negative bus bar and then clean up all the wiring. In the interim, however, here is what I did.
1) Bought two feet of 2/0 black battery wire
2) Bought three battery crimps 2/0 size
3) Bought heatshrink]
4) Bought some 5200
5) Bought box of stainless steel wood screws
6) Bought 2 stainless large wood screws
I cut the existing cable for the house bank behind the crimp and taped off the remaining stub of the old cable with heatshrink and electrical tape. I then crimped on one of the battery connetors onto the old battery cable and applied the heatshrink. I think fabricated my battery cable out of the 2 ft 2/0 gauge wire and remaining crimps and heat shrink.
I then mounted the shunt onto a block of mdf using the large wood screws (fender washers wouldn't fit...need to find smaller ones) and then used 5200 to mount that block to the wood in the battery locker, then connected everything up per instructions. The old house negative cable with new crimp to the one side of the shunt and the new fabricated cable from the shunt to the common negative. As it stands, the rj cable is still going across my sole...need a second pair of hands to help fish it through the cable chases, but I have my handy-dandy fish tape ready to go!
I then dry fit everything up, and it looks like I'm in business!
Two more projects have come from this project. First, I need to install that negative bus bar and clean up all the cables that are on the shared common negative. What a mess. Beneteau has done a spectacular job with the wiring elsewhere, but this just is worthy of a beat down.
Second, I have a voltage leak somewhere (as I long suspected). With everything turned off, I still track -0.25 to -0.5 amps somewhere. That seems to be a lot of stray voltage...no?
Lessons learned...a 2 hour project will inevitable take 7. Also, make sure you have a vacuum handy when you use a hole saw to drill through the wood...I forgot to have something catch the savings/sawdust...what a mess Lastly...if you want to do something right, it takes tiiiiiime.
I wanted to install the bilge counter today too..but *sigh* I guess it will wait for another day.