From: EXT
I would try some restoration epoxy. The liquid would be best to soak into
the rotted end by standing the board in a bag with the epoxy, the same
for
filling the cracks/splits on the other end. The epoxy putty would be
good to
fill the nail holes to keep moisture out once you have extracted the
bent
nails without further damage. It is not cheap stuff, but the roofing
company
should pay for it and your time to install it in a proper way.

I have used ConServe epoxy before - is this what you are suggesting?
Good idea to stand it in a bag - wood this old will probably absorb all
I give it. I haven't worked with the putty - I hear it's a bear - but
my painter will be doing it for me.
I think I'll be holding back ~$200 from my bill to cover the materials
and the extra time I need to buy from my painter. He's in the middle of
another restoration right now, but came by to have a look. He cringed -
but he also pointed out several dings they put in my NEW paint with
their ladders. All will be restored, but I'll have to deal with this
gaping void until the weekend.
It hurts to look at it.
Thanks for your help.