Sorry for the delay in response, I had typed a whole post explaining everything, and I timed out, which then erased what I had... I finally got a free moment to respond. I know when I got to this point I was scratching my head, and over thinking it. Carolina and Ichabod were a great help. I PM them with the same question and they steered me in the right direction.
So for the main frame it comes down to some simple Geometry, but in laymen's terms, my back of the boat (stern) was approx . 72" and the front (bow) was approx. 54". that leaves a difference of 18 inches. I made both my front and rear piece both 72" +- (whatever length made it lay on the gunnels from the bimini mount). this means I made a bend at 78" with the conduit bender because of the 6" offset. By doing this to the front piece as well, there was little chance of me getting the wrong measurement first time round.
Once this is done you can lay 2-3 pieces of conduit across your boat and then lay your bent pieces across inserted into the bimini ends (but not fastened). Now to cutting the appropriate length can be accomplished in a couple ways, by using Geometry, or by eyeballing. Your front piece will definitely stick over the side of the boat, so it is best to minimize this as much as possible.
because of Geometry rules your piece should be shortened by at least 1/2 (to at most the full) difference between the front and the back. If you don't trust that then use the eyeball method. line up the pieces and measure the difference between. then cut that measurement off of the front piece that attaches to the bimini end. Reattach and check for alignment, trim as necessary.
Once you have your your alignment, then you need fill the gap between front and rear piece with conduit. measure the distance and cut a piece to that length. Then I chose to use a piece of 1/2" inserted inside the 3/4" and split across the entire distance of the back frame, instead of just at the joint. Starting at the back, Figure the difference , make a measurement and mark on the 1/2", subtract the length of the EMT coupler (from each side) and make another mark. slide that into a the 3/4" with a EMT coupler cinched up on it, and then line up your mark you just drew at the end of the EMT coupler. run self tapper through the 3/4" and through the 1/2". As you work your way to the front space out self tappers through both pieces to keep uniform. Repeat connection at front end. I chose to then drill the whole way through my EMT couplers and attach with nut and bolt, but you could use just a self tapper.
For the height I knew I wanted it to be 3 ft. or under for several reasons, lower profile, still room to get up and move around, I needed 18-24 inches in front for dog entrance (i judged this off of height of a dog blind). My transom is 21', so I found a piece of wood/metal etc. and cut it to the height that gave me my number (3 ft) for the back, and used it to hold the back frame up by placing it between the gunnel and back conduit frame.
Once I had this braced up and in place, I just cut a 10' piece of 3/4 in half, and inserted it into the front facing bimini mounts, lined up the conduit with the back piece and drill my holes for the pins. The following pics show it after the above has been completed. I then cut off the excess from the rear support. I was going to use conduit caps to plug them, but Lowe's did not have them in stock at the time.
Hope this helps, if you need anymore info let me know
I started to put a PPT together detailing most of my construction. (minus pictures, did not get them in there yet).