I have an Orion H2 sub that I want to build a box for to go in my new Frontier extra cab. Orion says it's pretty critical to use at least 1" thick MDF in building the box to make sure it won't flex. I'm just wondering if there are any other materials I could use that would be as strong as this but not cost so much money. 1" MDF costs like $60 a sheet, and weighs about 1200 pounds. Any advice would be great.