I have spent a bit of time with three Micro-Trains and Kay-Dee 40 foot box cars to make sure that they track well.
I have also been playing around with structures, and I see the need to add an S curve.
The track in front of the green structure is the key to make the runaround work, there is enough room for a diesel switcher and a pair of forty footers, or one car and a 2-8-0