The short answer is, a rail mounted block won't get the MOB over the
lifelines. If he us unconcious or weak he most likely won't be able to
assist himself.

Remember you must be prepared for the heaviest person to go MOB while the
lightest is left to winch him back on board (250+lb and 100 +/- wife).

I don't like the LifeSling and have heard that people who are just
practicing with it (West Marine sponsored class) have a lot of trouble
making the system work.. There has to be a different way.. I only have one
because a 'gung-hoe' surveyor put in down on the recommended equipment list
which my insurance force me to get. (Waste of money for a singlehander)

However the LifeSling instructions require a that the lifting point be 10ft
above the rail (or maybe that was the deck edge) so you can get that
lifeless body inboard over the lifelines. The boom end is the only place on
most boats that will work and then you will have to lift the boom with the
topping lift. If you have ridgid boom vang, your scewed. A halyard is the
only realistic point that might give you the 10 ft.

I believe that the LifeSling also require that the line from the lifting
tackle be lead to a winch.

The whole lifesling system makes a lot of assumptions that aren't there in
the real world.

If you have a lifesling and have never gone through a West Marine course
(designed to sell, guess what??) then at least get it out and rig it up just
once for a good laugh.

Too often, now, I see the life sling bag/mount replacing the throwable
floatation device. ..


--
My opinion and experience. FWIW

Steve
s/v Good Intentions