Water supports the amount of weight that it displaces. Adding foam inside the pontoon will do nothing to make the pontoon support more weight. And weight is your problem. You will be better off adding a whole or partial third pontoon in the rear of the boat or move some of the weight forward. If it was mine, I would however fill the pontoons with foam for safety
Put the cooler in the front of the boat.
There is no 8.5pt COLOR: Black; : 'Verdana','sans-serif'; mso-fareast-: 'Times New Roman'; mso-bidi-: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA">buoyancy in the rear of the pontoons. Add a drain plug in both pontoons and fill them with a US Coast Guard Title 33 spec foam.
---} Get foam and instructions here {---
---} Get foam and instructions here {---