Hi guys, I'm a beginner and will wish to know if flat bottom on floats are better than the pentagon shape? And if you are friendly, want to know the
distance between the base of the plane and the top of the floats, so we can reduce the wetting of the engine?? Thank you!

The flat bottom floats will get up on step quicker and ride a little higher in the water, but in rough water they will pound the waves, where the vee bottom floats will cut through the waves better and probably track straighter. The general rule of thumb for height is the tops of the floats should be around 2-3 inches below the bottom of the prop arc. This will help in keeping the prop out of the water spray.
Seaplane

I find that flat bottom floats tend to skip on landing and that v-bottoms land more smoothly.  I use flat-bottoms on smaller planes that one does not taxi much, but just gooses the throttle and commits to flight, and the landings are more of a plop than a smooth swish. 

Here is a link to randy linderman's website.  It is the home of the Chuck Cunningham article that really congealed everything you need to know about floats.  Link

Thank you very much,guys!!!