I have my 5 different optima 7's with the antenna mounted in all different configurations. None of them have any interference or range issues.
I am using the spectra module in my 9C and have been thrilled with the performance. I am ordering the HPP-22 as JohnBuckner recommended.
I recently used a friends Aurora9 a few weeks ago, I will be ordering one of those also (that will have to wait for TAX season).