pre/post floats are the norm for every coastguard operation i've seen,
and having been involved in it its also something i do on my own boat.
I dont actually have a checklist with numbers on it, but i've got a
steady routine i go through with my boat. Checking the bungs, fuel
levels, rigging and sails is about it. Im the only person to use the
boat so i dont frequently go through all the items in storage, but i do
remove them all and check them about once every other month. More to
be able to remember what there is than anything else i guess.

As far as the batteries go... you can easily add an extra battery to
your existing one but put an isolator on it. This acts like a one way
switch, the battery can be charged by the charging system
automatically, but if the voltage in the system drops the battery will
be disconnected.

A true emergency battery should be as far above the waterline as
possible. While an isolated battery such as you describe would be
perfectly acceptable, I think there is a lot to be said in simplicity
for a dry cell set. Anything you charge may vent, overcharge, self
discharge, sulfate, etc. Dry cells replaced at proper intervals would
be very reliable and give you more flexibility to locate them above
the radio so you can be transmitting up to the last minute.

I don't know myself which way I will go but it's food for thought.

--

Roger Long