Allpro cover question: 400

I've just purchased a new T@B 400 and I've been looking at covers. Got a question for those with the Allpro camper cover or similar:

I had the dealer install a Fan-tastic vent cover over the vent and it adds about 6-8 inches of height to the vent by the look of it. It doesn't effect the whole top of the trailer - just the vent. 

Can the Allpro or similar cover handle that kind of "bump" and still be secured with the cover's straps?

Thanks, all.