I cut a 46 centimetre (eighteen inch) length of the plank. That gives a handle of about eight inches and a striking surface of about ten inches. That means the paddle will land across the entire buttocks, or the upper thighs even if the submissive woman has her legs a little apart for her paddling.
This means that although the paddling will hurt from the very first stroke, the second stroke will inevitably land on skin that’s still smarting from the first impact, and hurt much more. The most punishing thing about the paddle, I’m told, is that it’s so absolutely relentless. The site of the impact doesn’t move around, as it does with a caning, or a pleasure-focussed spanking. It just starts hot and sore, right across the buttocks, and then makes the whole area hotter and sorer.
If, as the dom, you want to hear and see sincere signs of sorrow and repentance, to to hear sincere begging and listen to the submissive’s fervent, urgent promises to improve her behaviour, the paddle is the shortest route to that outcome that I know of.