Hello,
I have been having similar problems. I am using jpegs exported from PS. I can not find a proper setting without having the picture squashed for the the way it looks in the preview window. It looks correct in the preview window when the “correct for aspect ratio” is checked.
I am not familiar with the PAR setting in Photoshop and have not figured out how to do it yet.
Thank you.
–Josh
Yoshes