Thought I'd get this approach out there since I just spent a good 3 hours trouble shooting my issue and finally found a viable solution:
To get some LH joists to be visible in our architectural reflected ceiling plans, I had to go in and edit the truss family. Set your work plane to one of the default center planes and draw an "invisible" model line vertically. Then set up a reference plane above & below the reference level plane, constrained with a locked dimension (I used 9'-0" just for reference ... I haven't completely vetted what the fall-out of different offsets would be just yet). Then load the jury-rigged truss family back into your model - and voila - the trusses should appear correctly in plan.
This is a technique I'll use from time to time when making custom families from scratch if I'm having trouble with graphic display issues. It essentially gives Revit something to "cut" (the invisible model line) and that is apparently the lynch pin for getting the truss to display correctly.
Hopefully this is useful info for someone some day. Or perhaps even Autodesk - who could in theory add this invisible line to the stock truss families.