To cut the back side off is same as not having one at all. We had a
terrific hail storm a few weeks ago, and I can not speak too highly
about the Max Air cover. The hail while not large was so dense that
looking out of the window all you saw was a solid white wall. And the
force of the storm hit the back of the Max Air and the inside vent was
all the way open and not a drop of water got in the bath room.
So if it wisdom you want, don't do the cutting.

Good luck,
Ed

Photo here:
http://groups.msn.com/CoachpotatosRVHomepage/yourwebpage2.msnw

Ok, I cut the grills out. Maybe a heavy rain might get in the coach
without the grills, but I don't leave 'em open most of the time and I
always have them blowing out, not in. I can now easily access the
outside of the vents for cleaning and the airflow is greatly improved!

The vents themselves are still well protected from wind at speed. I
really don't know why they have to have the grills. Maybe I'll learn
the hard way, but I doubt it.

The job was done with just a Dremel tool as the plastic is pretty easy
to cut away. I started with a jig saw but soon discovered that was
waaaay too much.

And it doesn't look so bad, at least it's up on the roof!

Dale