The bench is a bit too high, encouraging Robin to use the end of the blade with the least leverage
It's probably best to have an adjustable ring that one can raise and lower for optimum use, and help with the above problem. I have one of these. Robin's bench has the ring set too low
The side that holds against the soil should be square; and straight for maximum resistance, as the tapered side will then tend to force the peg tighter against the load bearing edge
The head should be rounded off beyond the depth of the notch to prevent it being split off.
I wouldn't use chestnut as it splits too easily when hit and tent pegs are rarely in the ground long enough to rot anyway
Ash was supposed to be best in the Dean but in the Chilterns they may have used beech, they used the draw knife there too as it was what the bodgers were skilled with.
It took variously between 11 and 17 or so cuts to make a peg.... with a peg knife.... I don't believe they were referred to as stock knives. I know one well regarded reference book says that, but there are so many basic mistakes in the illustrations that I regard that part of the book as worthless
Other than that, fine! Sorry Robin.