m-c - are you speaking about the "Surface (line) X/Z probing page"? - If so when you refer to a perimeter do you mean an abstract or pre-probed perimeter as opposed to a simple predetermined rectangle? Completely missed this option if that is the case. If you can find a moment and would be kind enough to elaborate. I would be very interested to explore this.
Please be aware that I have not physically used the feature yet.