All may not be lost yet. From what I can tell your interest is in the 3D probing rather than 2.5D and you'd just (ideally) use the 2.5D to produce the boundary for the 3D probing routine - is that correct?

If so, then you don't HAVE to use the 2.5D routine to create the boundary. You can create that by any number of means, even by hand and feed it into the 3D routine. Check out the attached image and you'll see what I mean. This shows a table with the object (the rough star shape) to be (3D) probed overlapping the table. The small circles show the points (at some arbitrary stepover) that need to be probed and of course the small crosses represent wasted probing in standard routines. The arrows show the points that you could enter into the triplet file by hand, in this case 17 of them. Depending on your amount of "waste" space and the complexity of your object you may find it worthwhile to try this approach. Remember your boundary profile doesn't have to be hugely accurate to cut down dramatically on the waste probing. This example has a saving of nearly 40% over standard routines (crosses / (crosses + circles) * 100)

This is what I meant, thanks.

I'll look into in depth over the weekend, thanks

Two questions in the mean time:

The triplet points, are they the exact object boundary or boundary offset by probe radius?

how precise do the triplet point have to be(within backoff)?

as for efficiency there is another point. Compared to the 3D pluggin: the pluggin reduces the stepover of one direction in relation to the ratio of the size of the individual values for X and Y probing area. So the time increases in proporion to the ratio of the probing area.