The 2% number is total daggerboard area, both daggerboards, based on total working sail area.
As I remember sol cat daggerboards, they are very thin. That is why they break so often. I doubt that you will be able to find any from another boat that will fit the sol cat daggerboard trunks.
The least expensive way to get sailing is to make some boards yourself out of vertical grain douglas fir, strong wood, and paint them.
Bill