Consider what you are asking: If I have a picture of a tail dragger sitting on the ground in 3 point attitude, should I build my model that way?
The simple answer is NO!!! CFS doesn't allow for adjusting the thrust line in relation to the centerline of the model. If you do the model with the floats level, you will need to adjust the thrust line. That in itself isn't too bad, but consider how you might have to adjust the angle of incidence of the wings and tail to make the model fly level. You REALLY don't want to have to do that. Just adjust the contact points and the model will sit level when in the water. Just another way of stating what Hubbabubba already stated.
Adjust the angle of the drawing! It is pretty easy with GIMP.