Paul,
I've been looking at this plan trying to figure out how to make it two loops like you want. The problem is its works out to be two tracks each with a reversing loop at each end. This requires at least one crossover at each end that will make unattended running of two trains iffy; you will have to monitor the crossovers all the time or set up an automatic stop/start system for each crossover that will keep the trains from colliding.
Anyway, here is a picture of what I'm talking about with the crossover (excuse my freehand drawing, I'm not too steady now-a-days).
Here is my attempt to draw the tracks on your layout design.
Anyway, I think it will be a bit complicated and you may want to look at other designs that give you two loops without the crossovers.
