Thank you - this is working out well.
I have a couple of follow up issues:
Once I have made the crosses large enough to see, and laid down the curve, the crosses are now a distraction.
Is there a way to select all the crosses at one time, so I can make them small enough to not be in the way, without having to change the cross properties one by one?
Or perhaps there is a way to create layers, so that the crosses are on one layer, and the curve on another.
A second issue is that a couple of the points do not seem to be entirely accurate, and seem to distort the curve a little bit.
Would it be better to simply delete that particular point, or is there a way to drag that point around a bit so that the perceived distortion is adjusted out of the curve.