When I decided on the stabilizers I actually went one size up. Most stabilizers are calculated with 10 kts as a reference speed and since I am doing only 5 - 7 kts I am below that reference speed. The higher the speed the smaller the fins can be, so likewise, the slower your speed the larger the fins should be.
Officially I should have the stab 20 for my size boat, but decided for the stab 25 and must say am happy with it.
Currently lying on anchor in a bay near Yalikavak, Turkey, have the stabilizers on in flip plus night mode, which means they will prevent the boat from going over the anchor and at the same time use less energy. The total draw at this moment is about 5 Amps at 24 V, I can live with that and the boat is lying rock solid in the water, won't move at all. The stabilizers only work when necessary, unlike a gyro that needs to keep on spinning all the time and thus draws massive amounts of electricity.
There is no way you can run gyro's off your battteries, you will simply drain them and that means running a generator 24 hours per day. If you calculate the fuel usage that is about 1 ltr of fuel per hour, which means 24 ltrs per day which is about 6 gallons. Over a period of one month that is 180 gallons. I can also do 300 - 450 nm of sailing with that fuel and must say that I rather do that.
While we are underway the electricity is provided by the solar panels and by the alternators, but even then I don't go over 40 Amps at 24 V and that is when it is already quite rough out there.
The one negative item is that you cannot combine bilge keels with stabilizer fins. I had the keels, they did not work at all for me, but in order to get the fins on and have unrestricted water flow over them the keels had to be removed.