Hi,
I have them on my '73 22-2, original factory installed. More nostalgic than truly functional compared to today's systems but they do work. The original design had probably 20 holes drilled in the bottom and at speed looked like a washing machine in there and overflowed through larger holes above the waterline. Pinfish, mudminnows, shrimp could make it, poggies would turn into chowder, just need crackers and scotch! I modified mine years ago by glassing all the holes shut in the bottom of the box and installed a through hull clam shell pick up and then installed an adjustable screen with a rubber plug so I could tame the water flow and it works pretty well. Plus they do act like trim tabs and help mine plane at about 23 mph with twin 115 Mercs which helps with 725# of engines back there. Also there helpful getting in and out of the boat when swimming. They actually look pretty cool and unusual by today's standards. I have a leaning post round well up on my deck for mullet or poggies.