I am using a Rodenstock Rodagon 4,0/60mm-WA for 35mm and 6x4,5.

For 6x7 I have a Rodenstock Rodagon 4,0/80mm and to be honest I can not see the difference in a 30x40cm print of 6x6 made by the 60mm or 80mm Rodenstock. Maybe when going up to 50x60cm but that comparision I never did.