Your bow hissing - does it only happen immediately after you come off the plane, and last about 30 seconds or so? If so, it's likely the air escape, although it usually sounds more more of a bubbling gurgle.
That sounds like chine walk. With 50 on the back of one of them it sounds like you have an almost perfect set -up engine. Do you have a tacho? It would be interesting to see what RPM you are making flat out, as it may have been propped for half a dozen heavy dive cylinders & accompanying divers, and is now revving way too freely. My humber was like that when I first got it. Simple temporary solution - throttle back a bit!
Might be worth having a play with the trim pin & see what happens. Remember if you are changing it either do what I did when I was messing with mine & get a bit of string long enough to tie it to the steering cable & still be able to extract it but short enough to go nowhere near the prop in case you drop it or only adjust it on a beach where you can reach the bottom!