Mark B,
I had a problem similar to yours last year with my 147. Lots of responses, they all made sense, but didn't quite solve the problem. Later, I saw another "identical" subframe that wasn't. It was still correct. Mine had been straightened by somebody, accidentally or to fit something else. There was supposed to be an more of an upward bend in the arms by the plate welded between the two arms going to the rockshaft. Maybe somebody had jacked up the tractor under the plate and straightened it out, or drove over it with a tank. I don't know. Anyway, with the arms straightened, the distance between the front and rear mounting points was now too long.
I would say that some heat in the bend area, the front end of the subframe in a vise, and a long section of pipe over the rockshaft end of the subframe arm would put the arm back to the correct angle. Be careful you don't twist the arms when you bend them. That, or drill a hole in the front attachment area of the subframe that lines up with a hole in the Cub Cadet frame, and put a bolt and locking nut through to hold it to the frame, ignoring the quick attach mounting. Worked for me.