Problem with AT 8" RC and new WO reducer/flattener

I just added a William Optics Field Flattener/Reducer III and a QSI WSG off axis guider upgrade to my AT 8” RC and QSI 540 camera. This added a few pounds to the load on the focuser (I am still using the stock focuser). I had a chance to test these new components a few days ago on IC410 and NGC281. The images show increasingly elongated stars with increasing distance from the center of the frame, but only at the top of the frame. The stars in the bottom corners are perhaps somewhat flattened (see attached). Prior to my adding the WO III and OAG the stars were much rounder throughout the frame.

Is this likely due to misalignment of the reducer/flattener due to flexure from the increased load on the focuser?

Attached Image:

Hi Arthur, it is probably due to flexure in the focuser. Do you still have the stock focuser on the AT8RC? They are really not up to heavy loads. I had to replace mine with a Feathertouch.
Do you have CCDInspector? If not, I think you can download a 30 day trial from CCDWare. Then it can show you much more about the image, including tilt and such.
Did you also put the Reducer at the proper distance from the CCD Chip?