Hi David, as Charlie suggests you should have a reading of the book from Dave Krieg, "building large telescopes". Your main issue will be the balance of this new scope. As you will discover in the book, the altitude bearings are fixed at a very specific point on the mirror box where the scope is balanced according to the weight below and above and the distance to the rotation center of the bearings. Shortening the truss pole will bring the UTA closer and the scope will become bottom heavy unless you get the center of rotation closer from the mirror, elevating the mirror box from the rocker. Another issue will be to change the angle of the split boxes as the short truss tubes will have a different angle on the mirror box. The last question is related to the size of the secondary mirror to avoid strong vignetting of your primary. Getting the UTA closer to the mirror will raise no issue regarding the inner diameter of the UTA. As far as I know it seems a feasible project that requires some initial calculation but you will have the pleasure to use it more. I have the UC 22 f4.1 and this combination gives me also a 3steps ladder so i know what it means. Best luck for your project Frederic.
Fr¨¦d¨¦ric Ruciak