I'm not sure what the ball joint is, have not seen one, I have a few brackets that turn the camera to a right angle like in the link below, the item on the right of the pic. I went this way on my sea kayak as the mount was between the rudder and where I mount my spare paddle, so it was easier to put the mount so the camera mounted from the side, also it lifted the camera a few cm's above the spare paddle for a clear view. I see my Fenn is quite rounded on the deck (but I have not mounted a camera on the rear of the Fenn), my Stellars are flat so I put the mount on the rear so that the camera slides in from the front or rear. My Fenn has a camera mount on the front hull, a curved one and the camera mounts from the side with the right angle bracket. The suction cup mount works quite well to on the flat front of my Stellars. So you probably need to buy a similar kit to below, I swear I have just about every available accessory but hardly ever use my camera
shop.gopro.com/APAC/mounts/replacement-parts/AGBAG-001.html