Well there you go. I was expecting ripples and dents laterally across the bottom, but it looks like you meant more of a hooking of the whole hull. I also see now what you meant by putting angle in the seams. For some reason I thought you meant in the channels on the floor. If the whole boat is hooking, I'd expect vertical wrinkles in the gunwale. Maybe reinforcement plates down the sides could help too in that case. You said you were going to use angle iron, but the picture looks more like aluminum to me. Whatever the case, keep in mind the lesser strength of aluminum and that iron will rust. That applies to the fasteners as well, but I'm sure you probably already considered that. Try it out and see what happens!