I am the least able rider posting in your thread. Regardless, here are a couple of things that could be helpful.
Post up your weight, height and age and other sports you do so that others can refine their advice to you.
And, you may already know about this resource, but if not, it is good for nomenclature and part numbers when you are searching ebay, etc. for parts:
View attachment 441159
IMHO, like
@Sparkplug says, don't change the hull. That's ski's highest and best purpose is as a 550. And no about of shortening or rockering the hull will make it better. Change whatever makes sense in the engine bay, but keep the hull the way it is except maybe for adding front and rear sponsons.
One of the members here has, IMHO, perfected the 550. Check out
@Aquaholic 's Mini Monster thread if you haven't already:
550 Stroker mini monster. [Insert Jaws theme music here].
www.x-h2o.com
Also, that Wave Hunters video posted by
@hornedogg79 is simply awesome. It looks to me that those riders were doing incredible things on stock 550 hulls. No doubt with highly modified engines.
The below video was put together by a member of the forum here. It is very playful and is one of my favorites:
You will likely move on to other skis, but a stock hull 550 is really a pretty cool ski to have in the quiver or to pass on to others. If you want to share your sport with others, it makes a great beginner ski. Here is mine:
View attachment 441162
BTW, you can still find, or have made, year specific stock graphics.