Road Glide,
The great folks (Local Amish) that put up my pole barn shop shell ordered the metal from their supplier for me to do my ceiling. They recommended and we went with only a 1.5" overlap at both ends. their opinion was and more than that was buying material I didn't need. Building is 66x40x14. Posts are 8' oc and 4' spacing on the trusses with the exception of two that are over a 10' wide door on the long wall. Panels were 3 rows of 16' 3" and one row of 18' 3". They feel very secure with just the width of the bottom truss cord as an overlap. Glad I didn't try to do it with just 3 rows as the 16 and 18' long panels were all I wanted to handle myself. I put up a 6 mil plastic vapor barrier before the metal and have R38 blown in cellulose going in next friday. I too had the builder install Tyvek house wrap prior to the wall metal. In my opinion it was money well spent as I can hear it rustle around when the wind outside picks up. Metal buildings have more air infiltration than I ever thought about. When I finish studding the walls, insulation (R-19) and drywall Im sure I won't hear it anymore but will help the insulation do its job. If your eves are vented the best time to baffle them to keep the insulation out is before the ceiling goes up.
Also a road glide rider here BTW
