All - GREAT photos! Thanks for contributing! These should help anyone looking to either upgrade or outfit their boat with LPG, or upgrade their existing LPG setup.
Looks like Christian has the new style tank connector, and I do like the idea of having some of the bits hard mounted with a high pressure pigtail, though if a leak in that hose ever occurred, that wouldn't be good. Some of the other setups with the solenoid, regulator and tank connector all on the same hard fitting may have the benefit of a lower likelihood of an unregulated hose breakage. But from what I've seen (other than the lack of gauge) all of these abide by ABYC guidelines.
In regards to sniffer, my shut-off unit doubles as a sniffer, and came with the stove, so I'm merely installing it since that's what I've got.
ABYC requires a shut-off within proximity to the appliance. My DC panel also has a "stove" switch (or it might be "oven" or "range"... I can't quite recall...) which would provide power to the sniffer/valve control, and manipulating either switch to off would shut off the propane valve.
On the locker drains, I'll try to snap a photo of mine below the cockpit (I'll caution you that firstly it will be much dirtier...) some time this weekend. I don't recall having that S-bend which seems to be causing you drainage trouble. If I recall it's a fairly straight shot out. Only issue I see there is in a following sea waves slapping against the underside of the overhang may enter more easily than if an S-bend were present. But then again when are you cooking during any substantial following sea?