Well, we undertook the tedious task of laying many sections of flex track to put in the hidden yard. My fingers are sore from all the joiners.
There are about 300 feet of track in the yard with the eight tracks. I have been able to lay about 90% of the track but I have had to stop as the other end sub roadbed is not in place yet.
I have used up all my joiners and a ton of track nails to get this all down. It took a week of effort but it looks good with the concentric circles. The radii grow from 62 inches to 90 inches. The is about a 6 foot difference in length from the interior track to the exterior track.
I used older Atlas track as this will be hidden and no one will notice the difference in color.