That's an earlier pic before I drilled through the deck, which ended up being about 4" inboard of the stanchion base (the one where the tank is mounted). There are, in fact, two fittings there: one for the LPG hose, for which I used
this, and the other for the solenoid wires, for which I used
this. Both the hose as well as the solenoid wires are protected with corrugated hose protector, then use black zip ties to keep them together.
You're right, it's not the most attractive in the world, and I spent much time considering how to go about putting in an LPG system on a boat that never had it. In the end, I decided uglier was better than trying to figure out an in-lazarette solution, botching it (the real fear!), and ending up with a boat in pieces.
Even so, I don't think it looks so bad, especially with all the other stuff that get put back there (there will be more!), and feel even better about it each time I make coffee (or cook/bake!) on my stove and look back there. Yes, that's the exact bracket that I purchased. The bracket comes with the solenoid, switch, and regulator. Just add tank, hose (I had to get 35' of hose), deck fittings, and 12V wires for the solenoid!
A common argument you hear against rail mounted propane is that it looks terrible. But to my eye yours looks little different than other rail mounted paraphernalia such as life slings, radar, GPS antennae, dingies, davits, etc. I'm assuming the rail mount bracket is from these guys?
http://www.suremarineservice.com/001-749A.aspx
I can't tell from the photos where your propane hose penetrates the deck, what the fitting looks like, and how the hose will look when all hooked up. If you've gotten that far, and have a photo(s) I would love to see. I'm very interested in doing a similar propane arrangement.