A boat as light as yours is going to porpoise when speeding. That's a fact of life.<br /><br />Lots of good ideas above, but I doubt you're ever going to fully solve the problem.
On my old flatbottom I put an 5 gallon container of water ( one of those plastic gas containers you can get for 10 dollars)in the front of the boat. You can add or remove water to get the right balance - worked great for me at a minimal cost.
