Nothing on hard-copy, but I have extensively done Ronchi testing with 100-200 lines per inch gratings at focus during mirror figuring. My feeling is that the small errors, say, under 1/4 wavefront, are hard to see with Ronchi @ focus, especially if the error is smooth and spread out over many zones. Seeing is the pricipal inhibitor, causing an undulation of the Ronchi bands so that you must mentally 'average' them. If I can discern problems with Ronchi @ focus, them my gut reaction is, "bad mirror."
I think Suiter knocks Ronchi testing excessively because he feels it is so often misused, as it is. I like the Ronchi test at RC, I have used it for many years and can probably discern errors that others have trouble seeing. So, it is a matter for the amateur to develop test methods that work for him, and constantly seek to cross-validate against other test methods.
Mel Bartels