It's got to be cheaper to just buy the full transom in the first place. I think that bracket costs a fortune. Then you need longer cables. I can't imagine wanting to undertake that.
I'm a notch transom guy and I wouldn't have it any other way. I love my Parker, but I don’t' think I would have bought one if I had to have a bracket. I know a lot of guys here love the full transom. You can get a little bit of water on the deck sometimes but I don’t care about that it helps wash the blood off! And one of these days I’m going to put a little flap of rubber on my custom motor well divider thingy. Then I won’t have any water. It’s just not a concern to me what little water splashes over every now and then. If you back down hard on fish, it would surely be a concern. But I’d still trade better handling anytime for a little water coming in. Not sure exactly what you mean about you’re heavy load. I can say I have an 85 gallon bait tank that’s always full with a 160 qt. Ice chest right next to that. I don’t carry tanks so I don’t really know about that. I think I would take a few test rides before I started a project like that. You may find it unnecessary, but like you said it’s a preference.
Good luck and if you do undertake this, be sure to post lots of pictures. It's definitely a great project.