I have attached two 3/4" panels of MDF together, so the end result is a 1 1/2"-thick panel. I need to reinforce it so that it does not bow, so I thought of attaching a 1/8"x1 1/2"x6' strip of steel along the edge. Simple research has introduced me to Liquid Nails and epoxy glue, but I would like to also hear from the pros at SE. I am not going to have any holes in the steel, so that eliminates screws. I am going to have to go the adhesive route with this one.
Edit: I left out one of the most important details, which is exactly what I am doing with this MDF. The double-layer MDF is not going to bear any load. Instead, it's going to be used as a custom door I am building. Since the MDF bows, I need to find a low-profile material that is even more rigid than the MDF. At 1/8" thick, this steel strip is very rigid. I just need to find a way to attach it so it holds as long as possible.