I just spent the whole afternoon since noon till just now [including a 2 hour nap and a 45 min run
] drawing up a full scale plan which I can't say enough how useful it proved to be.
I determined that I can use a 1.83 inch secondary mirror which was confirmed with NEWT and for illumination field of the secondary, I used a computer program by Alan Adler (called Sec) which shows that I will achieve between 50% to 75% illumination for the secondary for a 2 inch eyepiece and 1.25 inch eyepiece respectively which I understand from Gary Seronik's website, a contributor to Sky & Telescope, should be good enough as long as it does not go below 50% at the edge of the field [which is roughly ½ magnitude]. He says at 50%, it will not be noticeable.
As a result of my full scale plan, I also realise that I must go with a 4-truss design because a 3-truss design makes one of the truss too close to the alt bearing with not much space for a truss of a sufficient width.
I have also determined the truss length which is 64 inches.
I am however concerned whether when the all the parts are put together would enable me to achieve collimation and if my secondary mirror will be positioned correctly to reflect 100% of the reflected rays from the primary to the eyepiece.