Anyone who has welded knows that stuff moves in the process. How much more when pushing, pulling, and twisting to get things to fit. The laminated MDF is to hedge against that.

Here are some photos of the DuVal windshield frame in progress. 

That frame with the wood in it got really heavy. I used the engine crane to put it in place. 

The spiritual lesson is probably that we get stretched out of shape pretty easily too, especially our character.  We need Jesus to be the force in our lives to do for us, that which we can not do for ourselves!