Richie
This hobby is all about tradeoffs so I'm going to throw one last option out there.
First, it is possible to do this using all 036 switches but will likely require some 031 curve sections, IF you can live with the entry switch protruding into the tunnel portal, OR if you can stretch the width from 48" to about 52".
Second, if one of those is possible, do the same thing at the bottom and have all pass throughs.
Have fun