Bulletproof
I know nothing at all about printing. However there is a lively debate or two in the Xara X forum re these problems. Most people in the know suggest "The only safe thing is to export RGB TIFF and then do your CMYK'ing in Photoshop." I don't know if this is true or not. I'm sure if you posted this question in the other Xara X forum someone would be only to pleased to point you in the right direction. ( The question may get overlooked in this forum)
Egg