I really like the work you're doing on this. It really looks great!!
I do have a couple suggestions/questions though
Firstly, (is that a word

), check this
website I just found. Lots of great tips & tricks for where you're at I especially like the advice of welding your bracket nuts to the inside of the rail. Makes it real easy to assemble everything when you're done coating it. You should also check out
Art Morrison as well, because there are some really great shots, details, fab parts, & tips that you could incorporate if you wanted to.
I'm especially fond of the through-frame exhaust detail, because I want my exhaust to exit in front of my rear tires up in the quarter panel like you see on the Baja trucks.
Secondly, (I know this is a word

), I see that you are going to leave in the factory crossmembers & weld in the plate around it. My question is why?
We obviously have access to some fabulous fabricators here on this board, you've got the entire thing broken down, just have some custom crossmembers built up that do EXACTLY what you want to do, where you want to do it.
Don't get me wrong, what you're doing is awesome, & I'd love to have a place to be able to break mine down that far myself. I don't know if I'd have the ambition to finish it, but at least I'd get to work on it that way. Anyways this isn't about me & my lack of workspace, I digress.

I just recommend that while you're at this stage to "let it all hang out" Fully box that sucker front to rear, & in the areas where you need crossmembers, have DIY4x build you the same type of crossmember that'll bolt-in in between the rails. Then, not only will you benefit, but all of us first-gen guys will, because there will be more stuff for us to choose from because of the time you & DIY4X have taken as a result of this project. Those custom crossmembers that he builds are awesome as you know, & I'd LOVE to be able to set my truck up with several of them up & down my frame if it's possible.
You knew there would be some kind of selfish motivation there didn't you.

You do the work & I'll benefit from the experience. I'm all about the vicarious living.
Anyways, the project is totally awesome, but you're at a point where you can go over the top & it not be obnoxious. I say go for it!