I have had similar luck (though no test such as sinking) with replacing foam in the front compartment of our Montgomery 15 with 2 liter bottles. I did this because the previous owner had installed a car battery in the compartment without firm mounting. As a result, every wave, and every trailer bump served to make the battery further pulverize the foam in the compartment into ball bearing size pieces. It was a mess. Once I got (almost) every little piece of pulverized foam out, I filled the compartment with Costco lemonade bottles. They are fairly tough and haven't seemed to deteriorate at all. David GrahBishop California Message: 6 Date: Wed, 5 Sep 2018 19:32:32 +0000 From: Kevin Sandwick <ksandwick@hotmail.com> To: "montgomery_boats@mailman.xmission.com"     <montgomery_boats@mailman.xmission.com> Subject: Re: M_Boats: montgomery_boats Digest, Vol 187, Issue 3 Message-ID:     <DM3PR16MB0569F4085C2C2B7366762527AA020@DM3PR16MB0569.namprd16.prod.outlook.com>     Content-Type: text/plain; charset="us-ascii" Re-Styrofoam Floatation A fix I learned on the Daysailer (O'Day) website when the original foam got saturated, Remove it all and replace with 2 liter soda bottles. Each 2 liter bottle provides 4.4 pounds of floatation. I filled the inner hull with bottles and felt very comfortable that my 575 pound boat would stay on top of the water if capsized. Your mileage may vary! Kevin M-17 # 400