Track Seperation

[claycts]

I understand the NMRA seperation for height over rails. BUT what tickness are most using for the combination of SUB-roadbed, Roadbe then top of rail.
I amlooking at: 1/2" osb with 1/2" homasote then cork (about 3/16thick I think THEN code 83 on that. That gives me a sandwich 1 1/4 to 1 3/8 thick depending on the homasote. IF I go with pink foam then that is .5" osb, 2" foam, .1875 cork then code 83 now we are at 2.25" thick. IF track "A" passes over TRACK "B" in a no scenic location that would put the rails at 4.25" or 5.25" depending on sub-base. Am I correct or out to lunch? I was thinking of a "BRIDGE at these points made of .125 thick ? then back to normal thickness. In the OLD DAYS hidden track was kust cork on plywood and visable was the whol sandwich. Thank in advance for the help. (My wife got me the book on Model railroad benchwork to refer to)