To save my back when lifting half barrels on and off my pickup truck I
am trying to rig a hoist. I am planning to run a 2x6 across several
joists attached via lag bolts in my garage with a heavy duty eye hook
in the center. I will then use a 500lb capacity chain hoist connected
to the 2x6, connected to a custom bracket that fits between the handles
on the keg. The keg will only be suspended by the hook for a couple
minutes at most to give time to either pull the truck out when
unloading a keg, or pull the truck underneath the keg when loading.
In both cases it will be cranked up just enough to hover a couple
inches above the truck bed and then be lowered to the floor. The full
weight of a full 1/2 barrel is about 160lbs.

Does anyone see any reason to be concerned with the structure of the
home? The joists are the bottom of trusses in the attic that support
the roof.

Should I use a larger board such as a 2x8? Would crossing two joists
be sufficient, or should I cross 4 joists?

Also, the ceiling of the garage is finished with drywall. Does it
matter if I run the 2x6 on the finished side of the ceiling, or is it
better to run it in the attic? If I run it in the attic, it will
obviously look more attractive in the garage but the eye hook will have
to have a couple inches on it outside the board it is attached to
accommodate the width of the joist and the thickness of the drywall.

I do something similar in my basement to load the chest freezer
converted kegerator. I have a steel cable wrapped around a iron beam
and the chain hoist is connected to that.

Thank you in advance for any suggestions.