You should post a Scarm picture and SCARM file so folks without Windows or WINE can give some input too. You may not find an exact ready made plan for that size, but smaller ones built on a bigger footprint just allows for improvement and adding what you want.. Stretching most layouts is easy.
Your build should reflect how you run your trains; "Set it and forget it"?, heavy interaction with accessories? switching cars? Do you run more freight, passenger? Era? Are loops good enough? Is there a certain angle/action you like (e.g., I like a sweeping S... and I think he is asking about trun dia. for visual reasons.
A fully elevated line was great. I thought I was just "out of room" and trying something new too. But it has become my favorite line other than big engines look silly up there 
I kinda have a self imposed 4 driver steam or a switcher rule for the elevated, though the PRR K-4 pulls some time in the clouds.
With your 5' section on the wall, everything will be pretty accessable. Not so with the 16' on the wall though, and so two drop hatches for derail access would be smart.
I'm reminded of an early set of dropdown hatches on Gramps layout being left open and serving as "kid corals" where we watched from 
The elevated line WILL hinder your reach more. And you will lean on it, so build it sturdy and it will be a leaning rail for reaching center. 
You have to consider the thickness of your el's track's underside....the support system+rail height+tallest cars&engines. Any pantographs or trolley poles for electrics? What set my height was: (#1) a set of extended pantagraphs (GG-1, E-33) on O (tall). If raised by accident, I didnt want them bent. A raised rocket launching car (or lowered/is still tall at the tail fin!), and a loaded Evans Auto-Loader. Later an Erie Bucryrus Crane car caught some overhead action on occasion.
Having room to park trains without still being on an antii-collision turnout leg can be an issue (you can overheat switches that way). Don't underestimate the usefullness of a long siding, and or yard (and consider a transfer table vs turntable to space save on yard area if you like that)
The oveall viewing height should be considered too: Reasons for a high table are bringing the surface up to ease working on it without stooping and bending. Look to a very high table for an easy "ground level veiw". Scale folks especially love that. But I found even at 38 mine wasn't low for enough for small kids, nor for casual viewing from a couch by many adults, which when lounging on a couch, leaves the ground level view at 30-36" slouching/leaning or about 36" if upright. I was at 36". Too high for a couch view, I cut my legs to 33". Ok but I wanted 30". I added wheels bringing back to 36" 
... and would now loose four shelves 
I felt I needed a destinatiion for the el rather than it being just a loop on stilts, never reaching ground level. I didnt want a grade because I like to "set it and forget it". So, I used a hillside as the elevated's "landing pad",with a ground level tunnel running under the hill too.
