I didn't want something that would have no strength or be repeatedly dislodged. The bulwark is not strong enough with the small point of contact. So......
I chose two brass tubes of a size that suited my eye that fit each other.
The thinner tube I fitted through the deck down to the hull. This is fixed with fusion adhesive.
I used set squares to ensure perpendicular.
The second tube I have cut to a height and bunged one end with beech dowel and sanded off. Drilled a 2mm hole for the brass peg. Used 2mm styrene for the securing plate that will not need to be glued to the gunnel. So it is demountable for painting or whatever else.