You have any nice, large Oak trees with suitable limbs?
I might do the joist thing but I'd have to see what it looks like up there.
I would not do two lag bolts. Maybe one big eye bolt rated for at
least 500lbs through a hole between two joists that bolts through a
4X4 that straddles two joists.
An appropriate hoist load bearing point is like porn, I know it when I
see it but it is hard to convey.
I recommend a chain or strap and two guys lifting on each side with a
5 or 6 foot 4X4 and one guy or gal to help guide the load.
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