any shelter used for a generator, needs to be open for ventilation and air movement.
i have a bed cover on my Avalanche and i simply leave the tailgate down and take the front section out so that it allows for air movement.
plus the bed covers and truck bed provide some sound damping.
and Zoe the Wonder Dog(R.I.P.)
'07 Roo 23SS pushing an '07 Chevy Avalanche
Equalizer WDH and Prodigy BC