Dear Dustym,

The focal length of the lens is not your problem. If lenses that long can hold an 8x10 in focus from edge to edge they can certainly handle 6x6 negatives. While the lens could be defective, this definitely sounds like alignment. Procedure? Your manual should have that in detail. You should be able to get it pretty close with a good level, but a quality optical aid would be better. (Zig-Align and Versalab are the only two I know of.)

Neal