Challenges Gluing Up The Top Of My Roubo Workbench

I'm almost there! After hours of hand planing the edges of rough cut Oak, I have nearly achieved two flat mating surfaces for the glue up. When I first checked the joint fit on the two massive slabs, I had a slightly convex surface on both halves, leaving me with no gap in the middle but 1/16th inch gaps on both sides of the middle. So, needless to say I started planing down the hump in the middle being very careful. Rather than just explain where I'm at now, lets go look at some photos of the situation.

Looks good right? So let's glue it up! Not so fast folks, the situation is not as good as this photo makes it look. Now I have wood to wood contact on both ends and a slight gap in the middle. Damn! too much planing. Now lets take a look at some other issues I will need to overcome before it's time to do a glue up. 

This shot is of the middle of the top side of the bench top. You can see I have about 1/4" of the bottom half that is not even with the top half. On both ends, the top and bottom line up perfectly, so it looks like the bottom piece is bowed just a tad. I need to fix this. My idea is to make a steel plate that spans both halves and has a couple of holes on each half big enough for some lag bolts. Then at glue up I can put the metal plate on the bottom of the bench top and drill pilot holes for the lag bolts. Then with both ends clamped flush, I can insert and tighten up the lag bolts pulling the two halves flush. Sound reasonable?

This is a pic of the bottom of the bench top. You can see that I have bark still along the edges of both halves that form a gap or valley. This is not a huge issue because it is on the bottom where no one will see it. Still, I want to do a repair after glue up so I am going to pour some epoxy in the valley then sand it smooth.

This is just another shot of the glue joint. You can see the gap in the middle of the bench top. On the end you see a fairly wide gap also but that is not an issue. I was having trouble with the planes digging in right on the very edge of the end grain. So I took a No. 4 and took the ends down a bit by planing cross grain on the end. That fixed the problem and I'll be cutting about 3" off each end after glue up so that gap will be cut off.