With 14mm bands you could cut them short at 350% stretch. Shorter bands means they should guide the shaft down the barrel more while still being way smoother than 3 x 16mm. If your setup was superior you wouldn't be thinking of changing it. If you look at koah fatback it uses 3 x 16mm bands but fires an 8mm shaft with 40cm over hang and people still complain that with that setup it kicks like a mule. And I believe koahs are weighted and ballasted as well.
Anyways, if the gun is a reef gun your running an overkill setup right now. 2 x 16mm should be all you need. Even 3 14mm is a lot for reef work. My buddies $1300 Custom Wong hybrid has 3 x 14mm and its a pain to shoot.. also weighted and ballasted