It seems to be a consensus among experienced twin screw
captains that
leaving the rudders amidship is good practice for most
maneuvers.
There are exceptions of course but having the rudders
amidship leads
to more predictable response in my experience.

Much depends on the size of the rudders.
Twin screw boats tend to have much smaller rudders than single screw for a
variety of reasons. Some of these reasons have to do with rudder support when
the rudder is not directly aft of the keel, others involve the reduction of
drag to achieve greater speed, and still others calculate the combined area of
both rudders.

In the final analysis, on most twin screw vessels the rudder has a very
marginal ability to change the direction of the boat through the water compared
to the application of unequal thrust from the engines.

I'll be out on a speedy twin screw boat later this morning to collect some data
and
get some photos. I fully expect that at crusing speed or better and with equal
thrust from the engines the turning circle of this 42 footer will be close to
1/8 mile in diameter. And that won't be particularly unusual. Obviously not
much rudder in play.

When close quarter maneuevering we consider the wind and current and compensate
for any significant forces.
Seems to make sense that one should respond with the most efficient and
significant force available....whether that's
unequal thrust, a big rudder, or an oar.