Hey Matt,
How much distance is the bottom of the engine bracket to the bottom of the hull do you have? The more the merrier for clean water to let the props run in.
Many alloy builders fail to make the drop from the end of the transom for their extended engine boxes. I think this is done for ease of fabricating by just extending the bottom plates to make the extended engine bracket.
The Armstrong style bolt on extended engine bracket that keeps the end of the bracket up and not interfering with the water as it gets to the outdrive is better IMO. A home made bracket or a bolt on aftermarket built by Armstrong is better.
If you see I should have mounted my Armstrong bracket even higher up on the transom than I did, but even that 3" space got cleaner water to the engine. I put a 1997 Yamaha 225HP on it a week after I got bracket bolted on. I also made the aluminum full transom backwash plate to keep the cockpit dry and it gave me a place to keep my batteries.
Here is an Aluminum Center console pilot console I built for my fishing partner Al a few years ago when I had my 22' Whaler Revenge with my aluminum hardtop.
Where does your fuel cell go? And how much fuel can you carry based on that location. Does it sit above the floor or does it sit down into the vee section of your hull? If it sits on top of the floor, I would consider making a custom vee bottom tank and make it sit from the bottom of the hull to above the floorboard up as tall as I could go to get maximum fuel capacity.
Where will you be putting your batteries, under the transom splash board or are you going to remove the transom splash board and make yourself a new across the transom box to hosue your batteries, live bait well (maybe 40-gallons with rounded corners) and six or seven rod holders???
IMO I would go for a forward leaning window aluminum mini pilot house console with extended top and a center rear top support colum with a couple of rod holders on it and bench seat with food cooler built in it.
In your case, on the outside, I would weld the new bracket to the new transom plate, then I would make a piece of 1/2" thick aluminum plate as wide and tall as possible to go on the inside of your transom . Then I would bolt the bracket on.
What are your plans for the new cockpit floor?
I would also weld in dual gussets from the bottom of the console wide plat plates to the forward and rearward frames to strengthen theose wide flat plates. One of the other viewer on here had a problem with them already being broken/cracked where welded.
Oh Ya, I was half an alloy man, three boats and many years before I built my girl. Marty