Here is the deal. I am looking for some advise and possibly a boat builder.

Recently I purchased a new 70hp 4 stroke for my 16' boat. The problem I am having its the boat is way to heavy in the back. If 2 people get in the very back it can go under water. I moved the battery and gas tank to the front for ballast and it still is alot back heavy. I have taken approx 300 lbs of sand bags and put them in the front of the boat and it seems to equal out the boat. My question is :
Is there a way to add extra floatation to the exterior of the boat to account for 300 lbs?
Any thought or suggestions would be appreciated.