Kontiki sea trials

We have revamped last years RNLI Raft Race winning raft "KONTIKI" with new sponsons.  The sponsons were fine but the boat, despite a new coat of paint leaked like a sieve.   The danger is that the new sponsons having less bouyancy will not aid the the boat in staying afloat.   A lot of water came in last year  so I'm wondering whether they actually stopped us sinking in the end.