Firstly, thanks for all the comments.
I realize that the design needs a little tuning, especially the stand. These designs are all experiments, they start out in my head, then go onto some paper, and finally I make them. In this case, I did deviate from the drawing, and it wasn't for the better.
Yes, it would probably look better if the supports were a little thinner overall (but same width) and had a linearly decreasing thickness from the centre towards the three tips. Something to remember for next time. Another variation I can see is to have 4, 5 or 6 legs, but for anything more than 4 I would probably have to use a constructed stand.
I am pretty sure about plum/damson, that's how I got it from my tree surgeon and I still have a 4ft piece of it with bark on (ends sealed with paint and plastic sheets).