1" is BEYOND OVERKILL! They only use 3/4" plate for a dual engine bracket where the engien mounts to it. For what your doing, bite the bullet and go to ebay and buy a jack plate. I seen several manual ones on there for under $200. By the ime you buy a piece of plate, and do everything your talking about, you will be into it for just as much i bet.

While 1" may well be fine 1/2" angle would be stronger

I haven't mastered the art of conveying sarcasm on the internet yet, sorry.

So I took your suggestion and went to ebay and found a Vance JPL 4400 for $174. Never having heard of them, I looked up Vance and found their website and description of the jack plate here:
Vance JPL 4400.

There is a 3" setback version, too (JPL 4300). Both are rated for 225HP. $174 is their normal price! In stock and made in the USA (a plus in my book)

That price makes it pretty hard to justify DIY cost savings.

Buy that thing. Looks to be a high quality piece.

Not to mention an American owned small business. I'd rather give the little guy a few more bucks.

Hard to disagree with that, especially since I worked as a mechanical engineer/facilities mgr for the company that brought you 3 Mile Island and owns Forked River Nuke Facility. But you have to remember that we're talking compressive strength here, and for 6061 extruded aluminum angle it's 45,000. Since most of your forces are going to be compressive (The engine pushing against the angle which in turn pushes against the stern of the boat) you're going to have to go some to convince me that it's not safe to up the size of the engine. It's a long stretch from a nuke facility to an outboard bracket. Just sayin...

And yes, for the money, I would buy that mechanical jack plate. You can see the quality that went into the design and machining of it. Nicely rounded corners, all edges broken, etc. Def a piece of quality workmanship.

Got the new-to-me motor on the boat today. Not rigged yet. With the motor in the highest position, I think its pretty close to where it needs to be. Vance customer service answered my question within an hour or so. Actually Mr. Vance did (small shop). I get 1.5" minimum, plus and additional 4" of adjustable "up". So the jack plate will raise the motor between 1.5" and 5.5" I think it will work just fine.

I am ordering the JPL 4300 when they open up tomorrow. Good price, looks like a good product, responsive customer service, made in USA by a small business. They get my money and a plug on this site.

Will post pics when i get it and also when installed on the boat.

Thank you all so much for your replies to my questions.

Good to hear about the responsive customer service. Worth it's weight in gold these days.

Gonna post their site to the links section for the next guy who needs them.

Here are the promised pictures of the bracket and installed on the boat. I put the motor on the highest holes and set the jackplate 0.5" up. That puts the ventilation plate about 0.5" above the keel. I can move it up another 3.5" if needed.