“I’d also like to hear more from those who are able to fasten their track down solidly without encountering problems from expansion/contraction. Much as I would like to, I don’t see any way to accomplish that in the Maryland temperature ranges.”
I started my garden railway in 1992. My initial method was 1 1/2" concrete pavers, 8" x 16". I cut them to fit on curved track, etc. I then screwed the track down to the pavers. OK, so I thought. Within a few years, my method proved to be too labor intensive. Particularly when a change in track layout was required. One of the problems with track fastened securely to the substrata is expansion. Oh, my track expanded, but where the screws penetrated the ties, the ties split and cracked.
My entire railway now floats on ballast, just like the big guys do. My last bit of screwed down track went the way of the horse and buggy many years ago.
So in response to the question of securing track to some sort of ridgid bed, I would have to vote no. This is my opinion only. I’ve seen many modellers who have layouts with wood or concrete road beds. It’s just not for me.