How to make a grip on the shaft of your paddle?
I think the better way to do it is to create a handle over your shaft with the shape of your hand. In this way you can control much better the angle of your paddle. You can use this system in any paddle on the market.
To make it you need to clean the shaft with sand paper and alcohol.
Then, with two nuts of paste for car body, you need to create a grip with the shape you prefer using also plastic foil.
You need to use your hand to give its shape.
My advice is to make something like the one in the pictures.
Last thing, you need to correct your work with sand paper and make it smooth (again with 800 sandpaper). If you make holes, don't worry, you can put again paste to fill them out.
Enjoy