I have the Yankee (the secret- forget the side-to-side instructions- shake the shit out of it) and Nikor (works better, same secret) tanks, but I have just recently taken to tray processing, and have had good results. Steve S is right- give the trays a shot!
By the way, I'm curious as to why folks seem to limit themselves to 6 or less in the tray, what type of problems are you watching out for?
The reason I ask is that, well I guess I'm too dumb to know any better, from using the tanks I got into the habit of working in groups of 12 negs (6 film holders). So that's how many I have been doing in trays. Yep, 12 :twisted:
I don't see any scratches by inspecting the negs...
...but then again I have not printed since I switched (working out an enlarger problem) - Maybe I am in for an unpleasant surprise when I get one of these tray-processed negs on the enlarger... :ermm:

Matt