We have a MaxxAir and two MaxxAir-II covers. Clearance depends on how they're installed. Specifically, where the attaching screw holes are drilled into the vent flanges, which hole in the MaxxAir brackets are used, and how the MaxxAir brackets are bent.
I think the best fix is to remove the covers and bend the brackets a little. Remove the brackets to do the bending if you must, but I think it can be done with them still fastened to the flanges.
Might also be possible to put a couple plastic spacers (or stainless flat washers) between bracket and cover, but I wouldn't cut or grind on the cover.
If God's Your Co-Pilot Move Over, jd
2003 Jayco Escapade 31A on 2002 Ford E450 V10 4R100 218" WB