Full axis will maximize resolution. I use full aperture with my 8". It is a glass filter, but that won't make any difference if you are going to us Baader film. Probably simpler to make full aperture too.
I will be using Baadar film, but the directions in the manual suggest doing off axis but for a little 4.5" it seems like you wouldn't need it. How is the Baadar film compared to other films and the orion filters?