building sliding barn doors

[ugabulldog]

This is for my shop, (no animals). My plan: The style doors I am buildng with plexiglass windows: http://www.precisebuildings.com/buil...easure-barn/31

I was going to build door using treated 1x4's inside and outside with panel siding sandwiched between, butted not lapped http://www.homedepot.com/p/Unbranded...8869/202057810

On inside of doors, should I run top and bottom window frame boards all the way to outer 1x4's to tie all the panels together or just stop at window edge?

Doors should not be too heavy (5'x9' each), how far should I space brackets holding box rail?