Do you have a proper fairing block on that transducer? Before I put a new hole in the hull I would try to make it work where it is. I really can't picture one of these lead sleds getting that far out of the water. Look at
www.airmar.com they probably made your 'ducer and may have a fairing block for it. When you say forward bulkhead do you mean the engine room bulkhead? My transducers are just ahead of the engines and I have no problems, but so far my best speed has been 19 kts so this may not be relevant.