Post-tensioning the 8 foot lift-up walk-under span: For the walk-under lift-up section, I used regular 2" polystyrene foam (not the one reinforced with fiberglass facings). The span sags about half an inch, which is not much, but it does change the vertical track tangent at the ends. I epoxied two cable holders to the underside of the span near the ends, and tensioned the bridge with a steel cable. It's pretty much perfectly straight now. The tension can be adjusted. Some pics: Tensioned Cable Anchor And Tensioner Cable Anchor Tensioner Gluing the Anchor Sag before tensioning
Slight hiccup: ME #6 turnouts are significantly longer than the NMRA #6 turnouts in the XtrkCAD library! Back to the drawing board....
Ouch! How about the Unitrack #6's? Since you're already gonna use the Unitrack double crossovers... Hey, "in for a penny, in for a pound!" Disclaimer: Unitrack is all I ever use. Well, there was that fleeting flirt with B'man track, which actually drove me to try Unitrack!
Here is a comparison of the two layouts, first with ME #6 and second with the (non-existent) NMRA #6 tournouts. I could of course also chop one inch of the frog ends of the ME turnouts, which would make the yard ladders more compact, similar to the NMRA #6 layout. Each turnout adds about an inch to the ladder, which makes the track alignment at the south end a bit awkward. But the space is there. Here is the layout with the shorter (non-existent) NMRA turnouts: