QTR-Quadtone RIP

I'm trying to print an approximately 4x6 print on a 5x7 sheet of paper but the print ends up like what looks like a cropped portion of maybe an 8x10. The print is at 100% because I sized the original to be just the right size.

I'm using an Epson R1800...  I ended up using the original print, which was larger, then scaling it to about 66% - and this fit the 5x7 frame with some border.

Why wouldn't my first method scale properly at 100%? (hope this all makes sense!)

Thanks all,

Paul