Sea Ray 360 AC Hull Design question

[msi84]

I own a 1985 Sea Ray 360 AC (12.6' beam), and have re-powered her with T454s Gen 4s, formerly T5.7L and 71C trans. The hull design of this boat is quite unusual. She has quite a deep keel descending almost straight down from the bottom of the dead rise aft of the bow entry point and ending approximately 4 feet forward of the stern. The area just aft of this keel is dished inward (upward) almost like a bowl. The shafts exit the hull in this dished out area. I might be able to get pictures if needed.
My question is that she likes to ride bow high more than most Sea Rays despite the full extension of the tabs, and the economy isn't as good as it should be. I have tried to compensate be running with the water tanks (located under the aft cabin beds), empty or near so, and have also added almost 600# of sand bags to the bow storage area. This has somewhat reduced the need for so much tab, but it seams like this much ballast maybe adversely affect my fuel economy. I have dual Flo Scans and get approx .5 nm/gal @ 19Kts and 3400 RPM. I am currently running 24X20 three blade DJX Nibral props. I had the engines dynoed before installing, and they are right on spec , 450ftlbs @ 3200, 330hp @ 4200 RPMs. I have 2.57:1 BW 72C transmissions. The hull is very clean (thanks to Great Lakes fresh water). How does this dished out area affect me economy/trim, and should I add or remove the ballast.