I've a feelling it's in the rear bumper (fender in US?).
If it was within the HRW elements then the radio wouldn't work when the roof was down under the steel bootlid (or is the bootlid not made of steel?!)
I am absolutely itching to get my Eos...you cant imagine.... !
Ive learned so much from this forum already so should be well versed in all the little things - aerial a case in point - & all its little nuances.