RE: Why not very many tri float designs?
Well one reason "not to use them" is they don't do that well at high speed,, Most who do use them,, Like me, will install them an a slow flying type plane. See what happens at higher speeds is the floats want to lift the nose because of the way they have positive incidence to the wing and trust lines.
My first was a top flight Elder,, slow flier with a flat bottom wing a lot of fun until I let a buddy with little experience fly it. [:@]
The current one I have is a nitro planes e-stik,, It has a symmetrical wing but still can fly pretty slow. I know if I get it going too fast it wants to climb and pitch up a lot. I've thought about mixing some down trim with the throttle, but haven't experimented with that. I just fly it as is.
The Uproar might work well,, you won't know until you fly it.