Mark,
Thanks for the note on possible sagging. Most of the lengths are no more than 3-4' with 1/2" plywood. I saw one or two spots that might sag and once I get track down for a first look I plan on putting in a few more 2x4's for support. The current 2 x 4's are in spots where they won't interfere with track. The additional supports might interfere so I am waiting to put track down first before adding them.
I have been trying to keep things moving along, I haven't had a layout in a few years. Once the I got the benchwork up it kinda lit the fire. Also my wife thinks a garden layout would be nice out back so I plan on going outside in late March to start that.
thanks for the comment, they are all helpful.
Paul