In my case the teak box enclosing my tanks (almost) butts up against the turtledeck that covers my sliding companionway hatch. With the two tanks oriented fore/aft gives me oh, approx 2 feet between the forward side of the box and the mast. Orienting two tanks athwart-ships (port/stb) would allow for a little more room between the box & mast but being thus wider will hinder visibility forward. I've never felt 'cramped' in the (rare) times I need to get to the downhaul.
The regulator and propane solenoid is located at the tank(s), inside the box. A heavy duty rubberized low pressure hose (and solenoid wiring) exits the rear of the box into the front side of the turtledeck and makes an immediate turn outboard to port. It then makes a turn aft to run down the deck in the space between the turtledeck and the companionway hatch slides (plenty of room for a hose in there).
The hose then exits the turtledeck at the rear and makes an immediate turn outboard. The hose then runs to a right angle pipe-fitting that serves as a 'thru-hull' in the cabintop. This fitting is located right next to, just outboard of the handrail and under the cover of my dodger. Lets say approximately at the most forward end of the 2nd 'opening' forward in the handrail. Right in the corner of where the handrail exits the dodger. The hose is attached to this pipefitting via brass fittings both topside and below. The solenoid wiring simply 'penetrates' the deck alongside the pipe fitting. I don't particularly care for that approach and feel a watertight 'cable clam' would have been preferable even though it would require extra deck space to implement. Because of this arrangement (in my case) special care needs to be taken with regard to sealing/waterproofing. Still, it's never presented a problem (I just hope I never need to replace the wiring).
I like this location since the handrail offers some protection, it is out of the way, takes up virtually no cabintop space under the dodger and is thus also out of any direct weather. I suppose you could make an argument a better location might be in the same location but inboard of the handrail instead allowing it even more protection from getting bumped, being a toe stubber, etc. but since it's under the dodger it is already out of the way of such inconveniences. Plus, it would require a tighter bends in the hose as it exist the turtle deck.
At that point the propane thus enters the cabin and a second hose (attached to the pipe fitting underneath the cabin top) then runs downward and outboard (port side) within the (optional) cabinetry over the icebox. From there it drops into the portside galley cabinetry. Once it reaches below the countertop it then runs aft thru the cabinetry behind the stove finally exiting just behind the stove. The solenoid wiring continues from there to the engine room and then to the panel breaker.
None of the routing is that critical, i.e. space constraints, etc.. The only 'tricky part' seems to me to be how the pathway penetrates the deck. I don't think you would want the hose or solenoid wiring alone to penetrate the cabintop. Having a 'thru hull' with fittings on the hose both above and below allows for easy hose replacement should it ever become necessary (it hasn't yet)