Lynn,

Another thing I suggest you consider. If possible, put your engraving at the very top of the CorelDRAW page.
The less movement in the engraving process, the less likely a slip will occur. For instance, if you have a page size of 6x6 and put 2" of copy in the center of the page then the cylindrical attachment will rotate (at aggressive speed) for two inches before it starts engraving, then rotate (at aggressive speed) 4" to get back home. If you put your copy at the very top of the page then engraving starts immediately and you've reduced your aggressive motion from 6" total to 2"!

This is even more critical if you are engraving objects with significant handles(large military beer mugs, for instance) that add uneven momentum when reversing directions.

I understand that this requires a bit more "figuring" to determine the positioning of the glass when you need to put engraving at a specific location on the circumference, but for most glasses that doesn't matter and this will be your best solution to reduce total rotation.

Lastly, I've never been able to tell that engraving glass twice gives you better results than engraving once at twice the power. So as far as I'm concerned, the best solution is to determine your optimum speed/power settings for one pass engraving; which might have been what the tech was trying to say.

HTH,