Well I did read your initial post n SOME of the answers offered throughout the pages with your comebacks.
I really can'st see where your mysterious lines are coming from except you are using an 80mm lens for 6x6 n 645 where a 75mm is more appropiate.
BTW The "lines" you refer to are the non-image bars outside the framed area which look like slots in the easel blades? Get a 75mm lens n tell me if your problem goes away?
Are you in NYC?.. PM me, come over n pick up my 75mm n give it a try?
EDIT: Something just hit me.. do you need to adjust your condensers for different formats?