We have resurrected the old On30 layout. It has been expanded to 5x8. Am impressed by how much six inches improves the space. We are going to use Kato HO Unitrack. The benchwork is one piece this time, no sagging. Just added five foot cross members to the old side pieces. Using foam to create the creek below level.
Originally I was going to do the layout in 55n3 using Kato Unitrack. Then I discovered that I could get three inch cl to cl with the Unitrack. The 55n3 effort will probably move to modules.
The Kato Unitrack allows the track to be weathered at the workbench. That was one of the reasons I haven't built a layout. Too old to climb all over the benchwork to do the track.
Found that a "dirt" ballast berm could be developed using Sculptamold mixed with latex paint. Here for our HOn30 project.