Older thread, I know, but had to speak up. What I am seeing for "spoons" here resemble deflector more than spoons. A spoon is very shallow and is not always the answer. The angle if the leading edge on your intake is very inportant. Too sudden or too steep will cause loss of suction and cavitation. You should not be able to feel any transitions in the hull forward of the intake. These will make turbulance. A keel is normally ok, as long as it tapers out smoothly at least a foot before the intake. The key here is to make it smooth and gentle. If you can taper it out over about a foot, great. If you are making your own intake, be prepared to spent a lot of time getting it right. You will be working with progressive duplex curves. This is not easy to do and get it right. The trailing edge of the intake needs to be smooth/rounded. This can be a bigger problem then the leading edge when trying to get out of the hole because the impeller is pulling lots of water and the boat is not going very fast to push water into the intake to the suction can pull air under the transom from the rear in some cases.
A deeper keel will improve steering, but will tend to cavitate more in turns.