FIRST FORMAL LAYOUT. I am planning an HO 18" radius helix with a 3% grade (2.5" vert. clearance - not NMRA standards for vertical clearance) but I am running 30-34' short cars & locos, (Bachman Shay or Riv. Heisler) - roadbed is (2) laminated 1/8" hardboard reinforced with Aramid fiber at the bottom to reduce deflection (300,000 psi as I recall). Feel free to call me crazy at this point before construction begins as I tend to push the engineering limits due to space constraints.