Honored Sir:

I concur with my esteemed colleague ][<en, but would also advise you and your
fellow coopers to lay in a large stock of a) aspirin b)money, and to plan on
taking long vacations next spring (assuming, of course, that the contractor
won't proceed until there are favorable weather conditions).

Alternately, and this may be even better advice, sell before the work is done.

BTW, my esteemed client is still thinking about your ridiculously high rates
to search the known universe for drawings that may not exist, with a  promise
of NO (count it, no) remuneration unless you are 100% successful, as they see
it.

Ralph