I suspect you would have a problem attaching the lens to the camera. I have an MPP mk7, which is basically the same, and the front end bellows frame is only about 70mm across. I think (but check to make sure) that the rear element of a 115mm Grandagon is nearer 80mm in diameter.
OK, so you could unscrew the rear section, remove the camera back, attach the lens/board, refix the rear section via the back of the camera...and voilà! You wouldn't get much movement though....
Try a 90mm instead?
Richard