Oso;..your project intrigued me,so I went to e-bay and found a starchoice 76cm dish.Actually,the arm looks quite similar in dimension to
DTV lnb tubes.could it work?my guess is you would have to cut a certain length off the tube to compensate for the adapter,find a way to skew the dish properly(not easily done),and hope the focal length is compatible with the dish curvature(remember...this dish is originally intended for a single lnb).good luck.