Panoramic Sunroofs and Towbars

Hello, I'm thinking after a brief flirtation with BMW of returning back to the Audi fold. Will I be allowed to I hope?
I'm looking at getting a Q5, but will want to use it as a tow car. I've seen all sorts of issues about extra cooling being required, so any advice would be of use. But, in the case of one particular car I am thinking of, it has a panoramic sunroof, and the dealer says that it may not be suitable for having a towbar fitted. Is this the case? I've just run through the configurator on the Audi website and after choosing the sunroof it didn't stop me adding a towbar. Searching on the net, there are some mentions of this, but is there any truth in it or is it some sort of urban myth?
Thanks for any advice,