With the exception of grades needing some work to lessen them, the S-O layout might be copied with a smaller diameter track to fit to a 4x8 vs 5x9.
Thor's trains has quite a few old track plans to go over as well, but a search should pull some others up as well. I haven't had much luck with finding any dealer layout info online. Mostly it leads back here and is too fragmented for good researching (plus my os hates our search menu.)
If you run windows, download the free version of SCARM(better) or Anyrail (easier) and see if it fits, check the grade's max., etc.. I miss playing with them.
Not really a suggestion as much as just showing SCARM and an outcome. (a bit cramped for op.s, but I'm a looper anyhow. 4.5x9; S-O outer loop, O next , and 0-27 on center & elevation. In scarm, the 3d view can be spun on screen and zoomed in on too. The softward helped me stuff it all in.
It was also supposed to be ran from the other side. I just liked this view better once it was up and running.(scenery adjustment wasn't hard)
And railing along the longer straights on this side was also far easier than in the S curves on the backside 
plus with a half wall, you can always walk to the other view here.
