Interstingly, when developing my layout i experimented with curves, never having ised less than 3' radius before. Of the 11 rtr locos tried only 5 were happy on 5 coach trains @ 2' rad. The rest slipped on 3 or more. This was at scale speeds. Fortunately for me, most of my locos are kit and scratchbuilt and will pull the house down. I am not being argumentative, but if i were building on that scale, the curvature and access would be no no's. Most of that branch is inaccessible . Wheres #72 is more maintainance friendly. One or two lift out scenic portions and you can get at everything from above
Even the branch behind the viaduct is more manageable. Believe me, having built several large layouts i speak from experience AND mistakes