Mike,
I kept trying different track to find what you were looking to build. An outside passing siding continues the mainline circle and the through starts the siding, An MTH O82 brings the siding back to parallel. The track won't actually mate that way.
Is this what you were looking for - the outside passing siding? This stays within four feet wide or an 8' wide table.
If you don't have restrictions because of locomotives or cars needing large diameter curves- I can try using smaller curves and a smaller switch to make it work with all RealTrax.