Thank you very much for the reply, I will continue to check out other tools for this purpose, I worked on this last night and found out how to get a more accurate measurement so I thought I would share the technique I found in meshlab (I have not yet figured out if the "point picker" allows a far more automated "measure between points" tool [it seems too well designed not to have this potential feature]). I wonder if meshlab has potential for use with/as a geometric morphometric package.
Using the button that looks like a "line globe" (see where mouse is pointing in attached image) is the key to placing the two ends of the tape measure accurately.
1)zoom in as close as possible to your mesh, at the location of the first landmark you wish to use.
2) press the "measruement tool" button in the top menu bar.
2.a) click mouse on the point you have zoomed in on. This will place the first end of your tape measure.
3) press the blue coloured "line-globe" button. This interrupts your measurement tool, and allows you to do movements; use standard way of sliding, turning model, zooming out, then double clicking mouse to "center" on the spot on your model where you wish to have the other end of the tape measure land.
3.a) zoom in as close as possible to your mesh (you haven't yet pressed any button other than the blue line globe)
4) now your whole screen should be filled with the "second point for measuring" (the measuring line may appear to be coming from the "wrong direction" this is ok, it isn't).
5) now you press the "tape measure" button in the menu bar again, this "re-activates" the tape measure tool.
6) single click mouse on the point.
Presto- Your much more accurate measurement is provided (if the numbers are obscured by your mesh, you just need to press the "blue line-globe" again, and twist or rotate the model until the numbers are in clear view.
By the way; amazing results so far in both accuracy and precision, DAVID is an impressive tool with much potential for further uses, digital models provide greater freedom and greater precision in placing measures, reducing inter-observer measurement bias. I have a lot of work to go in a short period of time, but will share results as soon as I am done my little project.