I'm currently installing MTH scaletrax on my layout and have a section where I am using the flextrack. I have 1/4 inch cork glued to homasote which has been glued to plywood. The flextrack is used for two quarter turn curved sections of the layout, one is 48 inch radius and the other is 56 inch radius. I slid the rails to stagger the joins by at least 10 inches.
There are no commercially available rail joiners for the flextrack. I have found that the Atlas 2 rail joiners are a perfect fit for the center rail, and I've read that it is possible to use the Atlas 3 rail joiners on the outside rails but they require soldering. My concern with soldering the rail is that I will melt the plastic ties.
I tried sliding two sections together on the 48 inch radius curve (using staggered joints) and I found that all 3 rails line up very well without joiners. I attached a picture of one of the joints. It may be that they line up okay due to the wider radius. I have run some cars across the two tracks I put in and they have no problems. There doesn't seem to be any kink when you sight it by eye. I'll need 7 or 8 of the flextrack sections, at this point I plan to use the MTH track power connectors on each section since the rails will not be connected securely for power.
Has anyone tried this approach before? Any thoughts or possible problems doing it this way?