Thanks everyone, especially Jim and Seaplane. I hadn't thought about downthrust, which is considerable for the reaons stated, but it would help push the centre of drag forward as well. It was actually a mention on a thread in this forum of the step being too far forward causing the same problem that got me thinking about the water/float contact point while on step. I think the heel angle is OK. I never stalled on lift off, it just didn't look great. The relative length fore/aft of these floats is such that the tip is just even with the prop, but I never had a problem with nose-overs either. Not much expense involved, just lost air time.

I am contemplating building a new set of floats per the Cunningham guidelines this winter, not because I don't think mine can be made to work, but to make improvements to the tip position and the spray control (concave prow). Also, I found a little bit of water in one of mine and like the thought of a foam core.