Wonderful! Would you show us how you added the extra rail, please?
My Gauge 1 garden track Driehuis Junction was erected some 25 years ago. Since it was meant to run live steam I put the track at "table" height to be able to handle and control the trains. I added 0-gauge rail for 3-rail running to the inner loop of my track a couple of years ago. Since then my track is used a lot for Gauge 1 and Gauge 0, running clockwork, steam and electric trains. A selection of the running can be seen on my YouTube channel.
Since I have also some S gauge and some older tinplate 3-rail electric Gauge 1 locomotives the idea came to kill 2 birds with one stone by adding a middle rail to my outer loop positioned such that S Gauge and Gauge 1 3-rail electric could be run (not at the same time, of course). There was still one point/turn-out in the outer loop but that was not operational anymore and I started by removing that one. Then I ordered 30 meter of nickel silver bullhead rail and some 1200 rail-chairs from Tenmille, England (the supplier of my 1 Gauge rail which I used from the start). So now I had to drill 1200 holes, push in the chairs and slide the rail through the chairs and then I had to solder the feeder wires to each rail (bus wires run already through the track pans).
I do have some American Flyer S Gauge but also some German BUB Spur S; after finishing the track I found out that BUB Spur S is 24 mm gauge; so I have to do something with this BUB material to be able to run it also in the garden.
Regards
Fred