Rick, what you have done looks pretty good to me. What are you concerned about, safety? I reckon if you are able to attach a higher false fence to your reversible fence, and make an L-shaped fence to trap the workpiece on the other side, it will be as good as you can get, with your current setup. If you were using featherboards, you would need double-height ones to give you similar safety and stability as the L-fence I am suggesting.
About the radiuses, perhaps try what Nick suggested: rout a short edge straight through, without worrying about the radius, then the long edge straight through, then the other short edge. It will leave you with an edge instead of a curve where the channels intersect, but that can be softened with a few strokes of a round rasp - less hassle than trying to follow the radius.
Charles, like Rick I was taken with the idea of a horizontal table - I think Matthias Wandel had a design, and I also noted the one from MLCS. There was a particularly versatile all-steel model from an outfit called Hawk, I think. I even started gathering materials to make one, but did not proceed, as I was (and am) uncertain about the ability of a non-steel construction to handle the leverage imposed by a plunge router, particularly something beefy in the 2-Hp range. I only have plunge routers, and other than a trim router, none of them have the round-body spindle motor of say a Bosch 1617. I would be particularly concerned hanging one off of the plastic plate - I note you say to keep it as narrow as possible, but again one is limited by the size of the baseplate on a plunge router.
Which router did you use on your rig, and were there any problems with leverage?