Good choice of basement for the trains. regarding the layout height, i'd go with the 40" or even 42". To reach the corners if needed, buy or build a stepstool. this will allow you to reach the corners, and Nik can use it to stand on till he grows up--. Also, the higher benchwork will be more comfortable to get under for those times when working under the table is necessary. I set my layout at 48" so I could use it for storage and ease of use when it was time to be under the table.
Looking forward to seeing your track plan
A Day Without Trains is a Day Wasted
The only thing I would change is the one long bench 102 x 24. I would make it two benches 51 x 24 instead. This would give you the same bench but make it easier to transport.
Johnnny_reb Once a word is spoken it can not be unspoken!
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My N Scale laout is about the same size and shape. I used domino sections made of 1X4, cross-braced and covered with 1/8" plywood. The dominos are screwed to the wall studs and supported underneath with diagonal braces. The domios are screwed together at the ends as well as being attached to the wall.
I would recommend you consider keeping the width of the two 30" wide sections to 24" from the wall to ease reach in..
Chris