I don't know why I am so dense. I just did some rough calculations and it seems like 1.5 inches deep in the water would displace 5.7 lbs of water and 1.75" will displace 7.5 lbs of water. If the total weight of the plane is 6-7 lbs then it should sit in the water between 1.5 and 1.75" deep.

So still would like to hear what you all think on the 2 25's. Will they be enough? and will 1" prop clearance above the water be enough?