I have my printer set up with a templet for my art work I print a small yellow out line. Byond. My print area of what ever I am printing. That is the easiest way to do it i found as I make templets for the stuff I print on in my shop then all I have to do is drag and drop the art work in the template. And adjust. The yellow line serves to make print head to cover whole thing with uv light my templates are printed with 2 lines. On paper one line it in black for piece I working on so I know where to place them in bed 2nd line in yellow 3 mm from each edge of printer bed down both sides.. I learned it is easier to do a template for uv to match your program. As it takes all the guess work out..
Now as for a rotary for uv I use same steps. And never had a issue yet.
Thing is you have have 20 printers all same and no 2 will print the same . so. This is how I set all my printers up on printing. Remeber key thing in uv printing is a template. You get that right and set up. Everything else falls in place ..
I just finished a run of 325 wine glasses with no issues becouse of template. Just place and print.