Need some feedback about installing an exhaust fan in a skylight.

The large skylight is shared directly above two shower stalls and so I need something that will rapidly take the moisture away from the light well. Our HRV vent that's mounted in the skylight now is not sufficient to rapidly take away the moisture. I can buy a Nutone/Broan humidity sensing fan (QTREN100H) and mount it on the skylight wall but the manufacturer specifically says it's for flat ceiling mounting only.

As a potential workaround, my questions are:

a) has anyone here successfully mounted one of those Nutone's in a skylight wall?

b) would damage occur to the bearings if mounted on vertical axis?