So I've been contacted to post results. Here they are:
I had said that I was going to use a friends 40 ton press instead of a vac-bag, because I was concerned about little kinks in the steel not lying down properly. Little did I know....
I stacked my steel and plywood sheets in the truck, finding they were too long for the bed. No biggie, I thought, just going down the road. When I got to my buddies shop, the bed was empty. I frantically backtracked - no steel, no plywood. Then I noticed a group of framers who were working near my shop, and lo and behold was my pile, which they had rescued from the road after it slid out. It was dented a bit from having been run over once or twice, but I didn't have time to run and get another sheet.
So I really need a bunch of pressure on it, to iron everything out. Ha!!
Anyway, so I ended up using Gorilla glue, although all the glues performed fine - even Titebond II. I used Gorilla because they were the only manufacturer who told me their product was specifically formulated for dissimilar glue-ups like this.
Schedule:
Rough plywood with 80 grit, steel with 30 grit.
Trowel glue on wood. Trowel made from plastic laminate, notched 1/16 deep on bandsaw.
Mist water on steel.
Sandwich lamination between two sheets of 3/4 particle board (nova ply).
Press overnight (I'm sorry, I cannot remember what the poundage was set to)
Voila.
The press flattened all the kinks and dents from my "accident". I was able to bondo a couple of deep scratches since they were at the bottom and wouldn't affect the magnet.
Its been 6 months now. Although I haven't seen it, the customer would surely let me know if there was a problem - and I am scheduled to do their kitchen cabinets some time in the spring.