Huey,
Glad you found it useful.
A minor detail to be aware of... when drilling the holes for the T-nuts, they should be slightly offcenter by about 2/3's to be more centered on the leg. I measured roughly 80mm from the end that points out and away. But you can move it to the other side and have more extension on the bolt. Hope that makes sense.
Also, I chose balsa wood for two reasons, first I had it on hand, and secondly, easier to mold the slanted edges to allow the oval to fit the tube flush to the edges. But I suppose you can use whatever material you have that you can form to fit.
Lastly, I just caught a typo, the PVC pipe length was 500mm, not 400. You can adjust that to what you want as long as you ensure that it has enough material inside the tube to be stable.