Look Over/Help With Jack Plate Plans, Please

I think I've decided to make my own Jack plate since it will be cheaper than buying one, I can optimize it for my particular situation, and I enjoy and value creating things myself. I've read several plans on them, but the more I look at, the more my indecision grows concerning the little details. So please look over what I have in mind and please bring up any concerns you have or potential problems I might have overlooked or just not considered. Thanks.

To start off, the easy stuff: materials. I am going to use T6 aluminum angle/plate, stainless hardware and epoxy coated plywood for this project. However, dimensions and size are where my questions lie. I should note that I have a 1986 Evinrude 15 short shaft that I believe is 74lbs, and I currently have a 1232 Alumacraft flatbottom, although I am trying to sell the boat to upgrade to a 1248 or maybe something in the 14' range. Obviously I'll wait to start this project after my boat situation is resolved. I had planned on using 3"x3" angle @ 3/8" thick. I want to use the same size angle throughout to reduce cost, but is 3x3 enough or should I go with 3.5" or 4"? The layers I intend to use would be aluminum plate-wood-transom-jackplate-wood motor board-motor mount. Does this sound good? How thick should my aluminum plate, transom wood, and motor board be? I plan to make the plate/transom wood as wide and tall as I can to distribute the weight/force. The motor board and motor side of the jack plate should be limited by the size of the motor mount and how far I want to adjust it. This will also govern the dimensions of the transom side of the Jack plate, but I intend to make this part as tall as possible, again for vertical weight distribution. The holes in the motor mount should give me the hardware size to use for that, but I need to decide how many bolts and what size to go through the plate-transom board-transom-jack plate. I was thinking 3/8" or 1/2" hardware here. Last should be the hardware and how to mount the two jack plate halves. I've seen people doing the slotted hole/carriage bolts like in this sample:
https://www.dillon-racing.com/jackplate/plans/jack-plate-page-01.htm
But I can't help but doubt how secure that would be compared to just a series of holes 1" apart. However, it would be easier getting the holes to line up on all four pieces by doing the slots. If yall think that is secure enough, I will do the slots instead. Is 3/8" hardware good for this?

Sorry about the length, I just like to have everything thought out before beginning. Measure twice, as they say. So, please let me know what you think. I'll be sure to draw up plans of whatever we conclude here and document my project for a detailed write-up.
Thanks guys.

I was looking at recreating this exact same plan.
-I think holes in the jack plate would be more secure than the the slots. The holes (if drilled correctly) would help get the motor level with less of a fight.
-3" vs 4"; From what I've seen, most pre-fab jack plates have a 4" set back. Going smaller may create too much spray.... I dunno?

I think the plan we are both looking at gives all the dimensions and hardware sizes. The descriptions are vague but that's why they want us to purchase the actual plans.

Hope to hear about you progress. Good luck.

From some of the other ones I've seen, angle size doesn't seem to matter, and thickness shouldn't on small motors like mine. I've seen just as many people use 4"x4" as 3"x3" and even 2"x2". I haven't seen any complaints about spray, so I don't know that it has any noticeable effect. I will decide mine based on price, availability, and primarily how much room I need for my screw clamps.
Several have used 3/16" angle, but I think I'd use 1/4" just to be safe.
Looks like the only place I've seen hardware explained they used 1/2" bolts.
I've seen people use either holes or slots for both small and 175lb+ motors, so I think it shouldn't matter, just whatever's easier. Drilling all the holes would require the motor to be removed to adjust, so I think I will drill the outside angle and slot the inside. That way, I can use carriage bolts and just loosen the nut on the oustide to adjust the height, and I'll only need one tool to do it.

My setup is a15/48 alumacraft hondabf9.9d Vance 4000 jackplate. I started to build my own but this one is rated higher than i need is adjustable and only cost about 150.00 us. If you really want to build your own this one would be a good one to copy.