Fantastic (Dometic Ultra Breeze) Fan Vent Cover

[Mike3387]

After seeing reviews on the Fantastic roof vent cover, I bought a pair to install. Having a bit of difficulty because I just realized that my Montana has Maxxair fans installed and Maxxair fans have these premolded nubs. Has anyone else experienced this problem? I really like the Fantastic fan covers because they allow the most air movement when open, unlike the Maxxair cover that will open to about 50%.