I took some time to draw up the railroad in CAD in google maps..
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Yellow=benchwork
Black=tracks
Green=roads
Cyan=ocean
Purple=buildings
I first drew it to 1:160 scale which produced a layout approx 13' / 10' which fit on 3 4x8 sheets of plywood.
Then I modified the plan slightly rotating portions a bit to make a U-Shape similar to my first post of the screen shots. That got it down to something that would fit into an around the wall 12.5' x 8.5' bedroom.
The only changes I had to make were adding 24" curves to the tracks at the rotation points.
(we are still 1:160 scale except for the 24" radius curves)
I think you could easily get it down to an 8x10 bedroom with some selective compression.