If you're running where there are rocks, you definitely don't want a top loader grate.
This is what you need:
I have the spacing set so that the joint of my ring finger cannot pass between any of the tines.
Also, mine is set up with a push-pull cable, so it's a weedless grate.....this is an older picture of it before I added 2 more tines to the grate
Building it was fairly simple. I took the top loader grate, and cut out the mid section, only utilizing the shoe at the edge of the intake duct, and the block on the forward end where it bolts to the pump housing. On that forward block, I TIG welded 3 large lugs for my pivot point. The tines are made of 3/4" x 1/4" stainless steel flat bar, with the bottom edge ground to a knife edge (seems to help reduce weed fouling a little bit) and the top edges radiused.
At the forward pivot point, all the tines are joined together by a 1/4" stainless bolt that goes through the 3 lugs of the mounting block. A couple of inches back, I have another 1/4" cross bolt, to keep all the tines straight with each other. These cross bolts were TIG welded to the tines. As you can see in the last photo, at the rear end of the tines, the top side of each tine has a step machined into it. This step rests against the underside of the intake shoe. Set up in this manner, it prevents a strike from an underwater object from letting the tines swing upward, bending the control cable, and possibly letting rocks and other debris go into the pump.
Sea Doo jet boat weedless grates (at least on the '97 speedster I used to own) weren't like this, the rear end free-floated, unlike my design, which is more solid. My weedless grate design was inspired by the sea doo design, (and actually uses a few of their OEM parts!) but I improved on it somewhat.