You can still do your mods without a blanket and allow the expected room. If you look for the build pics of my car I have a ton of tubes in my floor and it's still light. I also have the tunnel and floor 'flanged' around the transmission. At some point it may be easier to do your own floor 'tin' especially if the old floor is cut out. With that said it's difficult to duplicate the 'shear-plate' strength of the factory floor in consideration of weight and integral strength.