The problem was unless one went down the ladder backwards (facing aft towards the ladder) the only spot you could get your foot, actually heel, was on the very edge, the white strip.
Plus, the edge had a radius on it which made for a dangerous combination. I don't know how the previous owner for the first 20 years survived it. When your feet were wet it was so slippery you couldn't even stand on it, with just your heel, facing away .
My wife slipped and fell all the way to the bottom, hitting her head on the left side. I also slipped with my right hand hanging on the the hatch runners, which made me swing around and hit my tailbone on the sink counter corner, breaking my tailbone. It took 3 months to heel enough so that I could drive sitting straight. And there were a number of other time that we had slipped but w/o serious consequences.
SOoooo, I cut out these half moon sections to allow ones foot to, at least, fit 3/4 of the way on the step. I used the cutout to reinforce the opposite side underneath for strength, since it seemed a bit weaker.
One other thing that it improved was I no longer hit my knees, which I would do if in a hurry going up the ladder. So it turned out to be a double advantage to do the cutouts.
And even with the cutouts the rounded edges were still slippery when wet. The plastic non-skids that the marine supply sells wears out so fast they're only good for a week or so of use. So a friend Steven of http://nomadness.com/ had access to some dock material that was installed at his marina and got a piece for me. Thanks Steve!!
So, I cut off some sections long enough to cover the front of the steps.
Ground them smooth, drilled and c'sank the holes for screws. BTW the material is a fiberglass reinforced PVC (I think) with a hard grit impregnated in the upper surface.
I cut out the radius part of the step and inserted the pieces in and installed the screws. Now all four steps have a non-wearing edges that definitely grips the shoe, and would probably hurt bare feet. :-o
And the finished product...................