Hey, I spotted you're in Warren. I'm Downriver, just S. of 94&Tel. myself. Still "313" 
And fyi, Frank's work is outstanding with a lot of deep thought applied if you aren't familar with it.... And to confuse us all thoroughly, so is moonMAN's (Carl) 
An under layout reverse loop will take away some area too. You'll need a about a 72-ish turnout to stay tight to the inner; or outer line( under the el line) for the grade(s)
If you run dcs in command mode it isn't as big a deal, but conventional and grades are work. As in throttle work. "Look Ma, no hands" looping in conventional needs block control to slow on a down grade or throttle up for a climb. Or you have to really be on the ball for the downhill or risk rolling in the curve at the bottom
The size, 16x5 is pretty good, but it would take all of it and more to get a "good grade". And you will need two grades for a reverse loop in each direction. IMO it would be a lot of work in a short time to do it all and finish before Christmas unless you really hustle.
I have a 7" climb over 15' and that limits what locos can climb, and how much even my best, can pull up the grade (about 10 hoppers with a magnetraction pulmor E-33. Some smaller locos cant even make it alone)
You will need about 7" of drop. I suggest you play with a grade for a day or two on the floor, testing your engines by pulling cars on a grade first, then decide.
I was thinking the dark track was the el, but the spur sidings are "the yard" aren't they.. I thought that yard was ground level...?
I'm gonna stop here on that, till you set me straight.
Three lines is easy enough to run, but four lines can be a bit much just in case your curious. I'm usually running 3 out of 4.
IMO a double reverse loop is really the way to go. Right through the town too. No stubs, just stop for an unload.
I did a single reverse and was sorry it wasn't a double in a week. I'm a looper and the ability to reverse both directions without touching anything would have fit my style of running better. My sidings are just eye candy, I don't really use them. I kind of knew it too, but conned myself. I guess it was to make sure, eh? After all, I'm not a kid anymore.(on the outside )
Actually I just watch the train. I was just as happy running on carpet. Diorama just happened to be something else I enjoyed as a kid. And my style is still toyish and abstract vs scale. I really only ever look at scenery when the train isn't running.
The narcissistic turn in this is actually in hopes you consider your own style of running and building a bit more while you can.
