Chuck Cunningham's articles are the holy grail of RC float Flying. The main article is available in several places on the net. Randy Linderman got permission from Chuck himself to post it, so I still refer to that link. [link]http://flyinglindy.homestead.com/skisandfloats.html[/link]
Chuck puts the step slightly behind the balance point.

Within a month or 2 of Chucks article which appeared in RCM, Ed Westwood wrote a similar but more techie article in MAN. He says to put the step under 40% of the MAC. For those of us from Tennessee, that means slightly behind the balance point. [link]http://www.smilesandwags.com/Floatsite/westwood.html[/link]

Andy Lennon used a line swept back 10 degrees from the CG to locate the step. that still puts the step slightly behind the balance point, but it scales better.

Ken Willard used a step location slightly behind the balance point.

Each of the gentlemen above have researched NACA papers, have built and published many airplane designs, and their designs and articles passed peer review, and were demonstrated thousands of times to work well.

Take a look at the Wipline website and you will see the Full-Size airplanes with the steps even farther back...approx 50% of the wing chord.
[link]http://www.wipaire.com/wipline/index.php[/link]

Now CowboyLifeSaver suggests that the only TRUE setup is with the step ahead of the balance point. One thing I have learned about float setup is that the "rules" are merely guidelines and things can still function properly when the "rules" are not strictly adhered to. This setup probably fits his flying style and his particular airplane. However, when I suggest setup tips to a newbie, I'm going to give him the guidelines to set his plane up dead center in the middle of what the tried and true practices are. CowboyLifeSaver's assertions that, with traditionally located step position, you will lose the ability to rotate the plane for takeoff are (as diplomatically as I can muster): incorrect. Still his setup works for him, and you probably won't get into trouble until your floats are far enough forward to adversely affect lateral stability.

I also don't agree with Cowboylifesaver's instruction to set up the float with the deck of the float parallel to the horizontal stab. The incidence of the horizontal stab is "usually" zero, but not always. If it's in the wing wash, the designer may have compensated by correcting the incidence of the horizontal stab to be zero to the local airflow in the wing wash. Roll out a set of plans for a Goldberg Eagle or a Telemaster to see what I'm talking about. Still- it usually works, it's just an inferred measurement. If you know your stab is at zero incidence, it can be an easy place to set a spirit level. The true, meaningful measurement is the wing's incidence should be 2-3 degrees positive to the deck of the float, if the float has a straight deck on top.

My particular bug about putting floats on planes is that newbies buy floats and then ask about setting them up. "I just bought a set of these huge heavy plywood floats from a big mailorder house and I want to know how to make my plane fly with them". I list several suppliers of foam-core floats on my website. Plane Fun Floats, Sea Commander, and Seaplane Supply, in alphabetical order. Foam-core floats are light, strong, efficient, and can't leak. I don't get a penny from the endorsements, I just want to see flyers succeed.