Hand locators didn't work for me, but silicone tape did.
The extra traction is perfect. Not too much, not too little.
I tried sanding, tapes, wax. They all failed miserably in the ocean.
Silicone tape is perfect for me.
I sometimes find myself just barely hooking with one or two fingers.
Other times If I need a bit of extra safety, just grasp a bit tighter. No death grip necessary.
I think the semi grippy tape saves me a lot of effort.
It might help with your slipping, it fixed mine.
My right hand would creep closer to the center.
If one of your hands is slipping to the center, it might be due to the stress of lifting the blade out at the end of the stroke.
My right shoulder is weaker at that motion, I think I was moving the hand in to reduce the stress of liffing the entire arm/blade.
If you take it to an extreme, imagine holding the shaft near the center.
A small flick of the wrist will get the blade out.
Ideally, you want to rotate that blade out of the water, but that's tough.
Anyone with a sore shoulder willl break that elbow early and lift with the biceps, rather than the back of the arm.
Maybe that's why you are shifting the shaft to one side - to favor a weaker shoulder, at the rear exit.
You can see how even pros adjust after a shoulder injury. They keep that ebow low and tight - rather than the typical K-1 sprint Olympian with their entire arms up around shouder level for the entire race.
This guy is a true expert and is doing online coaching for cheap. He's the guy I'd go to if I didn't have a local expert to bug. His videos are the best I've seen since Ivan Lawler's gym video. I think he's a physical trainer (physio) too. His videos really click for me,