[glend (Glen)]

As someone who has built both Newts and Refractors, I have some experience I can pass on. Normally production Newt tubes are not baffled, but it is blackened. Exceptions would be Mak-Newts, which have a large corrector at the front of the tube.
Even very large custom Newts do not bother with baffles as they are usually open tube structures, and a shroud might be the only external cover.
Refractors are usually baffled, and there is optical science behind the spacing and diametre of the baffles. Simply, the use of Ray Diagrams easily illustrate the light path to the eye piece, and you can work out baffle diametre and placement from the diagram. Three or four baffles are plenty.

Sure there are obsessive amateur builders that try to baffle open newts, who will argue it improves contrast; however the nature of Newts with front obstruction by the secondary, your already giving away significant contrast. A good front light shield is a better option.

In a dark site environment, baffles will do nothing for a Newt, in my opinion. In the city with nearby light sources that may shine into the tube, yes it might help; however a good front light/dew shield device is likely to be more effective, and it reduces the risks of fogging secondary mirrors.
I am sure you will get contrary opinions, especially in the Cloudy Nights forum section on ATM building.