30 is a lot. If you are willing to go with separate speed and
depth transducers, they sell a
depth transducer with a tilted element that will compensate for your dead rise. Your speed shouldn't be a problem.
Our old depth transducer was mounted on a 20* dead rise and we would have problems with it not giving depth readings in rough
water and not seeing as deep as the specs allow. The not seeing as deep was never an issue, but the rough
water was - we would be in narrow channels with
boat wakes and disturbed water that would prevent the depth from working properly.
Our new tilted element sounder works perfectly.
Mark