You guys are making it way to complicated. After 35+ years operating search areas with these, it has come down to the kiss principal.
3/4 marine plywood
Approx 3' x 2'
Tow line attached slightly ahead of center
Line has a quick disconnect, horse lead or even an old seat belt buckle
Elongated holes both sides for your hands
Off the tow line where it is attached to the board on the opposit side attach a line to a 2" piece of pvc pipe about 2' long for a bum board
This is simple, easy to transport and manouverable.
You can do cartwheels, fly upside down if you have the vis
Preferably your buddy is on his own sled right beside you.
Line signals to surface
One go faster, two go slower, three stop or go
The only way to search a large area
Marine operator uses gps for grid patern mowing the lawn
Have fun