My father wants me to haul the massive 42" whole house fan into the
attic just before drywall goes up in my home under construction.

We are dealing with a non-custom builder who isn't very flexible on
most things.

My dad says that if I hang the fan onto the roof rafters where it is
out of the way, nobody should care (it'll be out of the way of the
insulation guys) and it will save us the hassle of getting this monster
into the attic after drywall down the road.

Would anyone care to chime in on whether this should be acceptable to
the builder and is there any significant risk of theft ?

I am worried that the builder would discover this and not approve of
it, or it could potentially get stolen. I am wieghing that against the
advantage of getting into the attic when its easy to do so. I am
leaning towards not asking the builder, because the answer almost
certainly would be NO.

The fan weighs 91 lbs and I was thinking of hanging it off the rafters
in a temporary sling or something.

I believe we could install it after drywall goes up, but the different
between the opening we need to make for the shutters (47") and the unit
itself (46" square) is only ~ 1". My dad is probably thinking that the
unit is so large (46" square) that it might be difficult to move it
into that hole without damaging the drywall with the slightly sway or
jiggle.

Any comments appreciated.