@Steve Tyler Steve that sure sounds like a lot to do! That could take me a full year! LOL
Well, hold on to your hat, 'cause I had another over-the-top day (at least by my current standards!) . . .
First, having stripped the test layout of track and everything else, I lifted it off the sawhorses that I'd been using to elevate the formerly floor-level layout to mid-level height (about 32"), then installed 2X3 legs using lag bolts. The layout is ridiculously overbuilt, using 2X4's in a slide-together, two section format for the originally around-the-tree layout (which I screwed together when I repurposed it for permanent use a few years ago), and is correspondingly very heavy and hard to lift, but I persisted. Next, I covered the top with half-inch foam board, cutting and fitting the 4 X 8 sheet to fit the 6 X 5-1/2 top (using part of a half-inch styrofoam sheet to fill the shortfall, for those math nerds who might have otherwise objected that a 32 square foot sheet couldn't possibly cover a 33 square foot surface!
):

Then, I opened and unrolled the roll of Bachmann paper-backed grass sheet I'd bought earlier. Math being what it is, I *was* able to cut and piece the 100 by 50 inch sheet to cover the top. Unlike my main layout, I did not fold the grass mat around the edges and staple it under the top, but rather will use spray adhesive to adhere the mat to the foam sheet, and also rely on the split foam insulation tubes around the edges( as seen in the pics below). Pending such attachment, I put weights on top, to help uncurl the mat.
In a last burst of energy, I returned the track and accessories to the top of the layout, in a sort of test fit to find the desired location of all the animated pieces:


Tomorrow (the good Lord willin' and the tide don't rise!), I plan to finalize and mark the location of the accessory pieces on the mat, then remove them in order to cut through the mat and underlying foam board so the accessories can be recessed into the surface (most have thick fixed bases, which I want to try to 'disappear'). Then, I'll glue the foam board down to the top and use spray adhesive to adhere the grass mat to cover it. I'll then reinstall the foam edge, track and accessories, and wire everything up. Stay tuned . . . 