I tested the AR features yesterday and experimented with larger tracking markers (default is 80x80mm, I tested it at 160x160mm and 320x320mm). The idea is that by having a larger tracking marker it's easier for the software to track it at a larger distance without beeing limited by the resolution of the camera resolution of the Ipad.
This worked really well actually (marker at 320x320mm and scaling set to 25%) but it does require manual scaling each time you start the AR feature.

So I have a question and a tip,
The question: Is it possible to set a custom scaling value?

The tip: When you have tracking issues when trying to show a larger assembly with AR, try to use a larger tracking marker with a matching scaling setting