Just so you know, I made these mounts as low as possible keeping two things in mind:
1) Clearing the satellite antenna
2) Getting S-hooks from ratchet straps, etc under them.

When measured at the centerline of the roof:
The bottom of my load bar is 7/8" above the roof
The bottom of my load bar is 3/16" above the antenna
The bottom of my Rola cross rail is 1-5/8" above the roof (so you have basically 1.5" to squeeze your arm under there to wash the roof, pass straps, etc)

If I was just using a 2-bar system and didn't need to clear the antenna, I could probably drop it down 1/2" lower.... but it's so low as it is, im not sure it would really make any difference at this point...