General Design

Givens:
a. HO Scale layout of the Placerville Branch between Folsom and Camino, California as it appeared and operated in the 1930's.
b. small steam - the largest steam locomotive ever to appear on the Pville Branch were Pacifics 4-6-2 and that was rare.The consolidation type locomotive was standard SP power on the branch.
"Engines not allowed on branch: A-3s, A-6s, mikes and larger. But Pacifics except P-8s, 10s and 12s were allowed. Also T-40 number 2371 was not allowed. It looks like anything without a trailing truck was allowed plus most Pacific's." Engines types per a 1949 employees TT - thanks to Phil Smith for this information.  
c.11x29 room size

Druthers:
a. double deck design with constant elevation gain around the room - no helix.
b. code 70 ME flex track except in staging (code 83 Atlas)
c. 24" minimum radius .  Lower level nominal height 42" Upper level nominal height 62" Steps stools maybe required for the vertically challenged Operator. Since the lower level climbs to meet the upper level level, deck spacing gets smaller and smaller as the lower level climbs. At this room size I gladly gave up deck spacing to not have a helix.
d. some degree of prototype - not to the level of copy track for track - although that probably wouldn't be too difficult given the Placerville branch track main, spurs and sidings. All you need is a large enough room.  I am more interested in a fairly high degree of accuracy when it comes to industries served, then I am in accuracy of track duplication. And I really want to attempt to maintain historical accuracy in my modeling efforts. When visitors arrive I want them to know right away this is not modern times.

Level O Staging
Level 1 Folsom to El Dorado
Level 2 El Dorado to Camino