elevation with track

cork or vinyl roadbed is much easier to use than trying to cut circles from ply.. if you would like to save some $ you can create your own roadbed with "easy mat" floor underlayment and a simple jig using two razor blades.

"floor underlayment"

thought of that, but how do track screws work on this?

Displacement is not the only way to make horsepower. ..oh you meant trains.. well the scale guys are going to have a ball with your inches..(just shoot me)..but that stacking bit is basically how Ive built grades before (helps to have 1/8", 3/16, & 1/16" too). Block wired resistance and/or multiple throttles for grades for "look Ma, no hands" running in conventional. It was fun for me because I like to tinker. 

While I like a dedicated look, I cant decide on just one. I've been wanting to take a few smaller layouts, do one PW/semi-scale/plasticville, one tin, one 3R-scale, etc. then surround and/or interconnect them all with 2 fast running mainlines, and hopefully a use a big curve. I have three layouts that aren't too huge, 3.75'x7.5', 4.5'x10', and 30"x30". Plus Grandpas huge layout 12-14'x over 20'. Connecting those is a major thought lately. This will increase the possibility of taking something runnable with me should I ever move away again too.    

I don't think I have any level track on my layout, the world is not flat, as you say.  I've done what you say and built custom trestles to raise the track gradually, etc.  All of it works if you adjust it carefully. 

Did it way the hard and messy way. Made a paper template under the track and used it to cut out 1/2" plywood with a saber-saw for under the track and cut out a 1/2" inch of homosote for on top of that, joints overlapping. Laid down cork, and then screwed track down through cork to the Homosote layer. If the 1" of plywood and homosote (four scale feet) don't make enough room to make streambeds, gullies, etc, below track level, I can lift and shim the entire track to the desired height. Very time consuming - second level is still in progress.

"second level is still in progress"

are you happy with the results and would you do it same way again,  I am thinking along same lines as you describe, want to do it once and right.  time is time, well spent or not my way is kinda like your way  old school

 I discovered something quite by accident to create a non-flat track layout--warped plywood.  A thin sheet of plywood (3/8") was left out in my garage.  The moisture as well as its leaning on the side caused the sheet to bow.  You can attach such a bowed sheet atop a flat sheet of plywood with screws to prevent it from returning to a flat shape.  The train will go up the gradual grade and can go down the other side, depending on how you lay the sheet.  If the curvature is too severe, just lay the sheet down for awhile with weight on it or turn it upside down as you would place it on your train table and let it go flat somewhat.  Screwing it to the flat plywood will keep the curve intact as it cannot return to a flat shape because it has been screwed down in a curved shape.

One of my elevations is on a ceiling loop and uses block control with all four throttles on a Pre-war Z. 1/4 is flat ground level, 1/4 flat elevated, the rest is two steep grades (Lionel PW risers). On a re-do I would skip the two flat sections of track. Instead extend each grade to lessen the slope as much as I could. And I would only have use two of the Z's controls. 1 for uphill, 1 for down.

I think the stacking idea is a good one. The roadbeds are raised to keep the tracks out of water. (Fry AC motors). You have the ply and the time. I know you will artfully scenic the edges.

The continuation of the elevation to 0 in the rest of the layout may be more work. perhaps a berm opposite track\ditch that fades to 0.

Some place everything on 1" foamboard to make it easy to create relief and terrain. That requires longer track screws.

Midwest cork on the curves......I use a matching thickness foamcore board on straight sections and inside tunnels or areas not seen. Super easy to use over cutting any type of wood.

All that wood makes me wonder...Any old tubs of latex wood putty? I had some old dust contaminated stuff, no longer worthy of use for finish work. At Wallmart I saw a low cost food mold of bricks. Yep, spread it like icing on some scrap paneling till about 1/16"-1/8"thick. Then pressed it with the brick mold. Way oversized, even for cinder block. But painted brick red with weathering and foliage, nobody has noticed the size yet..shhh. It was fun way to create a "free" Hi-rail/tin-plate looking brick wall. Spread a bit thick for putty maybe, but I figure any future cracks make it more prototypical. And if it cracks, under the paint its close to the color of the inside of a brick..(about a year and none so far)