T&T: holding tank size

[badornato]

I am taking out a rusty microphor marine sanitation system from under
the bed in the fore stateroom and am planning to replace it with a
plain old holding tank and Y valve for simplicity's sake.

what is the best material for a holding tank?

and although this may bring up some personal questions about our
individual effluent volumes, what is a reasonable or optimal size for
a holding tank for usually two persons and occasional parties of 6-8
people?

the boat is a krogen 42..

-- 
bruce t adornato md