Secondary Size

I'm ready to order a secondary mirror for my truss tube project and need some advise as to it's size. The primary mirror is a Stevens 14.5" f4.3. My calculations are pointing to about a 2.75", trouble is standard sizes are 2.6 and 3.1". I'm leaning towards the 2.6" after talking with a few people, but wonder if anyone has any thoughts, or, if they might have a similar mirror what size secondary does it have? I'm mostly wondering about the illumination at the edge of my widest field EP, a 26T5. Also, I might someday get a 31T5, but I am satisfied with the 26T5 and it's exit pupil is smaller.
Thanks and clear skies,

Hey all of you Jims out there!

For these secondary sizing puzzles I recommend that you download the freeware "Newt." Factors like the tube/cage diameter and focuser height will affect the choice of "best" secondary size and "Newt" makes it easy to fiddle with these variables. In the end it will come down to a trade off of smaller obstruction vs. larger fully illuminated field. It always does!

http://home.att.net/~dale.keller/atm/newtonians/newtsoft/newtsoft.htm

Jim III

Stevens use to work for Carl Zambuto, and Zambuto mirrors are in Starmaster telescopes. My 14.5" f/4.3 Starmaster scope uses a 2.6" secondary mirror. That is the size I would use. Good luck on your project.