On a HO scale layout with double track, minimum 24" radius, a loop will come off the backdrop some where around 54 - 56 inches. How do people get access to the back of the bench with this depth and how do people transition to a reasonable depth layout without a severe s curve or a long portion of very deep bench? Any examples someone has would be helpful. Thanks.
Sounds like you need one or more access “pop-ups”. These will give you access to the far reaches of the layout. I think that pop-ups are covered in books on MRR benchwork.
A track planning book would answer your other questions. These forums are great but there’s no substitute for a few good MRR books on benchwork, planning, scenery, electrical, etc.
Here’s a simple pop-up access hatch:
