The filter is mounted in a carrier below the lens. I have two different carriers, both OE Omega pieces, one that swings away but is fixed in it's distance from the lens. The other does not swing, but can be adjusted up and down by means of alternate screw mount holes. None of these alternatives seems to have any effect on the rings.

The Omegalite cold light system does not provide for any head adjustment based on negative size. All you do is use the appropriate negative carrier, and the appropriate lens. The D2 condensor head requires changing condensors based on format, or the use of a variable condensor version of the head.

I have uploaded a scan of one of the problem prints to this site, for anyone interested in seeing exactly what I am dealing with. The rings are in the sky, to either side of the central peaks.