I’ve generally used L girder framing and then the “cookie cutter technique,” in which you cut the subrosdbed to follow the track plan and then use risers which attach to to the joists. This allows you to precisely set the the elevation as you want it to be. But now that I’m in my 70s and about to get disc fusion surgery, I’m not sure that I’ll be able to under the layout the same way, so I may have resort to a flat top layout. Sigh…Time. will tell.
But I can tell you that if you’d can do it ,
the cookie cutter technique will yield good grade and elevation control and accuracy.
Good luck.
Rubin
