Janus 650 roll up door order info

[over40pirate]

Looking for feedback on Janus 650 roll up doors.

I need a couple of 7' hi x 9' wide doors.
I heard that by ordering a taller door, it makes the gap at the top a lot smaller.
How much taller does the door have to be to create the smaller gap?
If just a few inches, would adding to the bottom of the header do the same thing?
I'm putting these on the ends of my 31 x 31 steel building, and not sure how much extra room above I have for a taller door.

Any info on this and other things about the Janus doors is appreciated.

 

[glider]

I don't know about making a smaller gap at the top. I do know that Menards sell the same door under the name Ideal. I did better going through Menards than buying direct from the factory Janus.