It is the DDM60 Lewis
Under good seeing and no cloud I have managed stacked images of 1.6” FWHM at 1.16”/pixel and 300s exposures
As you say, as long as the stars look good the guide graph is meaningless.
Not sure what Mike and Trish’s guide graph is like but if they can get 1 hour Ha subs with round stars at 0.65”/pixel, it doesn’t matter