I have completed a 1/4 scale Laier Taylorcraft with a 9ft wing span. It currantly has a Zenoah G26 with a hp rating of 2.4. I have recently decided to put it on floats. I fly off water at my cottage flying a Piper Cub with an OS 70. With floats the Cub is a little slow getting off the water but once airborn it flys scale like. Friends have told me that having the G26 for field flying would be just enough power for scale like flight but not enough for float flying. The floats I'm building are 47in long and I can see that this would be a lot of drag so I can also see why the G26 wouldn't have sufficient power to fly in this configuration. So my problem is what size gas engine and hp rating would be suitable for this plane? I have been concidering the NGH 38 four stroke rated at 3.8 hp. I'm assuming an increase in 1 or 2hp will provide adiquate power but I'm unsure. I need to modify the hieght of the float wire so knowing the engine and prop size is important before I install the floats. Also, under the tail of the cub there is a fin that was part of the float kit that I built for the Cub. I understand that this fin acts as a secondary vertical stab and aids in directional stability due to the air turbulance created by the floats. The Sig float kit doesn't come with one. Do I need to add one and roughly what size? Any help with these questions would be greatly appreciated.

i have a dle35 on my lanier tcraft and it would be fine with floats. g26 would be a bit anemic.. you dont need the extra fin. i have several cubs on floats both with and without the fin. the one with the fin will come out of a spin 1-2 turns sooner than the one without.
DO NOT DO THE 4 stroke.. i dont care what the paperwork says you will have less power than the g26...

You could use any of the DLE 35. G38 sized engines.
As to the NGH.. they seem to be out of stock everywhere and less powerful than the 2strokes of the same size.

The RCGF 40 twin would be an excellent choice here.

Like I said in your other post skip the NGH 38 as I dont think its anymore powerfull than what you have now. Go with a DLE 35 or the VVRC 40cc twin