Shelf railroad around the wall of my home office:  10' x 12'   Traverses three doorways and has a 3% grade on each of the long walls.  HO scale Bachmann EZ Track (hey - you stay with what you've got ).  Mainline has three passing loops with two that overlap; and a siding.  Shelf is corked and profiled to the roadbed.  So far: no landscaping.  Bachmann Acela set, Bachmann Digital Commander set, (3) Bachmann GP35 Conrail, Conrail / PC, Chessie and mixed rolling stock. I run two freight consists: The Santa Fe engines from the Digital Commander as a consist pulling a string of Chessie hoppers and the three Conrail GB35s as a consist pulling a string of Conrail, Conrail / PC and mixed boxcars.  I park the freight on the passing loops ( have to break the Conrail string into two of the loops ) and bring the Acela off the siding for a run around the mainline.