I'd been fighting my 8x10 Korona for a while now trying to figure why a 5.6 Symmar would make such mushy looking images and not getting anywhere. I got to thinking of several threads I'd read concerning tripod stability and LF gear and decided to work on the tripod end of the deal. I was using a 3021 Manfrotto with a ball head, a 3055 I think. It was supposed to be able to handle the weight, but I was having doubts. I had a 4x5 studio camera downstairs occupying a nice 3033 Manfrotto with a powerful 3047 pan head, using the same octagonal QR plates. Boy that sucker is heavy but it made all the difference in the world! I'm actually seeing sharp detail under the loupe now.
I found also for a heavy camera like the Korona the pan head is much easier to set up and level than a ball head. Go figure. As far as the QR plate there's one detail to be aware of. The regular plate with the knob and thumbscrew will not do. Theres a second version with a screwdriver slotted screw that also comes with several secondary screws arranged around the plate to lock it down from swiveling, which is very neccesary. You can't lock the plate on with enough torque using just the center screw to hold it from twisting, you'll damage the threads before you get a good grip! So far I haven't seen the standard plate with the extra screws but it looks like at least one threaded hole is present to add your own setscrew.