I got the book "Hydrofoils design build fly" by Ray Vellinga in the mail today. It looks like a very good book. I should be able to learn enough to make paravanes that work well.
There are human powered hydrofoils. A human is about 1/8th Hp and with the machine is over 200 lbs. My solar powered boat wants like 25 normal to 100 lbs peak pull. So this should be less than 1/16th Hp each, but I have 2 paravanes, so less than 1/8th Hp. The electric motor I have is about 3.5 Hp. The drag for the paravanes should be acceptable, if I get a good design.