Thanx Richie! (@Richie C.)
To answer your notes:
My recollection is that the 72W power supplies are DC only, so any engine or accessories you plan to run have to be DC compatible. Not sure about an 18v power supply but that is underpowered. If it were me, I'd probably go with a small AC transformer like a Lionel CW-80 or MTH Z-1000 and run it to a distribution block and then out to a number of power drops on each loop. Both of them also have a separate output for accessories.
Yes - my plan is to run only DC compatible engine or accessories; specifically, LionChief or LionChief+ 2.0 and only plug-expand-play accessories.
The 18W power supply would be only for the outer loop and for the train only. That is what I use today on my HP ready-to-run set.
You do not need to isolate, but if you want you could insert a 1 3/8 FT fitter piece at the two locations I have marked. If you do, make sure you disconnect the wire underneath.
Thanx on the fitter pieces; that helps. This would mean re-doing the outer loop to handle those fitter pieces, right? I don't think I would be able to "just add them", correct?
You can use manual anywhere you want and think it will not get a lot of use.
As I replied to necrails and regurgitating here for ease of answering - I am trying to figure out which locations would be the "low use areas". My thought are the switches that are in the elevated loop and also the switch that takes it to the passenger station. That is something I would like to confirm from the folks here.
Thanx!