Hi Roger,
I always thought 2 arc sec per pixel was the absolute upper and should be somewhere between 1-2 arc sec per pixel.
I am probably ignorant to this (Bock is the guru). My LX200, SXVH9 with Optec F7 reducer and binning at 2x2 produces 1.23 arc sec per pixels for me.
CCD Calc helps (you probably have it, if not link is below)
http://www.newastro.com/book_new/camera_app.php
Look forward to more informed replies here.