You took the words right off my keyboard!
It would make it ideal to add 6 to 12"s (when I get home the next time I'll take a photo with a ruler on the back of the rack) to the rack . Perhaps two 6" bars added on both sides of the center section to minimize the spacing between the cross bars, if you didn't want to add more of them also?
That with relocating or as Lekmedn mentioned about Adondo's mod of just installing a separate antenna would be perfect. (Adondo's Great Sirius Satellite thread mod fyi > http://www.jeepcommander.com/forums/...nna+Relocation )