I wish I had my old basement layout still set up, but I tore it down and have started rebuilding my layout in a vacated bedroom (kids are leaving our nest). I used and will use again 42" and 54" O27 curves and switches.
I really like the lower O27 profile compared with O Gauge. With 42", 54" and even some 72" curves out on the market, it's easy to use O27 tubular and not limit yourself small engines and rolling stock (though I have stayed with Traditional size).
Having had an O27 layout before, one recommendation. Find a way to convert your switches to pull from fixed voltage, not track power. I found 4 used K-line O42 switches that I will use on the new layout, but have read that the Lionel versions can be converted.
