Have you ever shot 6x9cm (you should be able to get a 6x9cm back for a Baby Crown)? I think of it as half way between 6x6cm and 4x5". I think the 6x9cm negative is a significant step above 6x6cm to make it worthwhile. Your 6x4.5cm negatives will seem microscopic 65mm is a really nice wide angle on 6x9cm.