A few thoughts regarding the last month's worth of posts.
Aisle width/center island - I thought that you resolved the aisle width with the full-sized mock-ups and determined that you would fit easily. I can't believe that you gave in to your detractors!
That is unless you tried the mock up some more and that made you change your mind. The pictures in post #65 looked doable.
Yes, the aisles would have accommodated my moving around, but I would be standing most of the time, or just setting at the very head of the peninsula. I would not have had even a small workbench inside the 'layout room'. These thoughts weighed on my mind while I was up in Canada.
I decided to do a modification to the original plan where I reduced the size of that peninsula. In doing so I gained extra width on both of the side shelves. In one particular case on the right hand side, that allows me to get that turntable/freight yard scene all in (the one I just posted). I thought a lot about the extra room I was gaining for both myself, and a small workbench inside the perimeter of the decks around the wall. I came back from Canada and did the modification to my cardboard mock-up, and that convinced me I had made the right decision.
Double track on RH peninsula - Do the math, double track, turntable and roundhouse will not fit. Your thoughts on using a shortened roundhouse is a reasonable solution given that you just want to display your engines. I doubt that it will all fit even with single track.
I was having doubts myself, and that's part of the reason I did that latest mock-up I just posted. Do you see the 2 radius lines in this photo,..those denote the C/L of a 23" radius inner loop track, while the outer track is a 25.5" radius one......
(articulated steam will be confined to the outer loop, while diesels can use both)
The brown circle of cardboard in the photo represents the 18.5" turntable pit.
The shaded area in the layout's corner behind the turntable and stretching half way down that side to the 'Mt Royal' train station is a removable 'city-scape structure' fashioned of artistic foam board that sits over the double tracks. The 'roundhouse' itself is only a front-faced structure probable 3-4 inches deep.
Ten gallons RR in five gallon layout - You have posted hopes of including the turntable/roundhouse, yard, wharf, steel operations, coal, mountainous regions, bridges over rails and roads and maybe some things that I cannot remember. It is going to be a bit difficult to make it all fit. Difficult but not impossible.
You are correct. I have so many structures I would like to include, but I will have to make some decisions as I go along as to what I might be able to include. I'm just trying out ideas on some major ones as they need space and feeder tracks.
Time - Now, please don't take the following as negative because it isn't meant to be. Stop overthinking and get on with building at least the lower level.
I know what you are saying, but time spent planning may well be time well spent. Its already caused me to alter my plan,...and I'm not sure I like the new track plan as much as the old one.
Funny thing is I may have to do considerable work on the upper level deck before I install the lower level,...accessibility. (and I don't even have its track plan laid out yet)
You have posted somewhere that you only spend part of the year in Florida and that you spend part in Thailand. Then you go and spend a few weeks in Nova Scotia (I am jealous); when will you have the time for this endeavor? Unless you have a very tolerant wife!!!
I'll go away for a while.
I have a tolerate wife as she is living in Thailand right now.