I run a single rudder setup on a Stossel hull. The rudders are 4 feet tall and 44" long, but true airfoil shape, which is roughly a 10:1 aspect ratio (4-1/2" thick). The rudder generates lift on the outside that drastically improves turning forces, it will actually pull the a$$ end sideways when applied. The true airfoil shape vs. the sharp nosed fake foil stuff is a key element in the steering authority.
The key issue with the large single rudder is windy days, invariable it's always a side wind. I have stopped and trimmed my trim tab to take the load off when I have a long run with a side wind, then reverse the setting on the way home. I am not very familiar with the Jimmy White, but I think it's a glades sled (??). The round bottom Stossel hull tracks well, I would be concerned about being able to fight a side wind with a flat bottom sled. In the sled situation I would opt for dual rudders, but true airfoil shape with top and bottom plates (the plates act like winglets on planes to hold the air on the rudder). It will double your steering authority vs. pancakes.