Sizing of rudders and turn fins

[mephiskapheles6]

I am building two boats, a 1/12 and a 1/6 scale hydroplane based on the Miss Supertest III design. Being new to this hobby I am wondering how I size the rudders and turn fins for these boats. I am also curious to know the proper set up for the strut, can I use a stringer type strut or do I need to use something different for a flat bottom hydro?

cheers,
corey