I have a metric file with working units of m, mm, 100, 80. I'm attaching a border as a reference and attempting to scale it up to 800:1, but it won't allow me to do it. The maximum scale it will accept is 500:1. Is there a limitation?
In J, if you attach a reference file without using a saved view, it can require a clip boundary before moving and scaling. When attached as a saved view, the view limits act like a pre-clipped reference file.
You might be running into problems if the design plane isn't large enough to accommodate the graphics. Are the working units of the reference borders the same as the active file? What happens if you create a cell from the borders and scale the cell up by 800. Does that work?