Those top loader grates are OK if you only run on open water, where there is chop (and no debris). On choppy water, they perform as advertised, feeding more water to the pump and minimizing acceleration slip.
But on inland rivers, bays, back creeks, and other shallow areas, or in areas where there is a lot of debris, a top loader grate is a horrible thing to have on a jet boat, because it's a vacuum cleaner, and at some point, will result in a stick or gravel being jammed into the pump. If it's severe enough, it could lock up the impeller and cause the PTO to strip out (as many of them are just threaded into an aluminum coupler)
Several years ago, I had to consider the pros VS. cons of the 2 designs, and I decided a top loader grate wasn't for me. But neither was a standard grate. At first I designed it just like the weedless grate of a Sea Doo jet boat, but then improved it a couple of times, by adding more bars on the grate, and then eventually re-doing it as a stomp grate with 1/4" spacing between the bars.
Will my boat run wide open in chop, or take a turn at full throttle without cavitating? No. But I've learned where the slip limit is on the RPM's for certain conditions, and adjust throttle accordingly. I may not have the performance in choppy water, but when I go across a shoal, at least my @$$ isn't gnawing bricks, worried about picking up an oyster shell, rock, stick, or other object and damaging the pump.
