THANKS for the replies to my post!
Basically, due to work commitments, my friend and I do not get together often enough to work on our present layout. Am making first 2'X4' drop-in section on 2" extruded foam slab. Peco TT, Atlas roundhouse and basic loco servicing facilities[coal/sand/
water/diesel fuel/ashpit]on TT lead. Since we use hollow core doors with 2" of foam atop as the basic units of our sectional, portable[take to train shows]layout, we can insert the drop-ins anywhere we desire by pre-planning track/turnout locations. We're both ex-members of same HO modular club from several years ago. We did use some drop-in structures on that layout as some members wanted to have the ability to change trackside industries to make Operation sessions more diversified.