SteveB wrote:
Just one more question.

Well, maybe two.

When I DO get this thing running, I want to leave off the center standoff
until I make one 200# lift, where I will measure the center deflection at
midpoint. Just for my own curiosity, and I say it will be less than one
inch. But I will surely do a slow lift, and measure it so that if it does
deflect a LOT, it won't fail with the load too high.

If that goes good, I will install the center standoff, knowing about how
much deflection it is stopping.

What other areas should I be concerned about watching/monitoring/testing?

I would want to give the upper support (where the davit is attached to
the building) some careful thought. If the davit were to come loose from
the building while lifting it could be quite impressive. If you plan to
use fasteners such as coach screws or expanding bolts, see if you can
find data giving the safe load for the fasteners. Choose them so that
you have a good margin of safety. If you can't find data, build a quick
prototype of the support from scrap materials and try to break it.

Chris