When you open the file in XCS you will see a second layer.
Thats my outline Layer its set to ignore. Anytime im making a tumbler of any size I use one of these.
I get my diameter and height of cup. Draw a rectangle set the height and width to my measurements, 
Make sure to unlock the measurements so you can change one without the other changing. 
Little padlock symbol between the measurements and set the box in place. This makes it so much easier for me to make sure my Image or design fits exactly into the space I have to use. Takes the guess work out of placing your image.
Frame your engraving before you start
Also I tilted the bottom of the tumbler up 26 degrees before I started. Took my distance sensor and measured distance from the middle of where the cup transitions from top to bottom
Amazon has a great digital angle level for $16.99 makes things easy. I do also have the RA2 and the RA2 accessory kit for adjusting the angle

If you dont have these. You are looking to get the bottomm of the tumbler as close to level with the top as you can  You can put some scrap material underneath te RA2 to achieve the same results. Just eyeball the line from bottom to top. I did that before I purchased the level and RA2 Accessory kit
Make sure your RA2 is stable and not wobbling and stable. Nothing worse than a wobble that the laser will make worse as it moves back and forthe especially at higher speeds