Fellows
Thanks for the kind comments. The layout is running better now than ever. Two pairs of 2 trains on 1 track has never been this reliable, just like running one train per loop.
I even had 3 trains on 1 track (on the long outside tracks of both train boards) for about 3 minutes, drawing about 4.3 amps on one LW, until a derailment! It will never work well since there is only one isolated track section and only one train can be slowed down by relay.
Charlie