I have a 2015, and I barely can fit in a 30 lb tank in the bay due to the mounting strap. Once it's in it looks like there would be room for a 40. Only if you change the mounting.
Measured it out and its not possible as the bay for the tank is too narrow... Even if you modify the steel floor to allow more depth the tank will not fit between the outside/inside wall (it barely fits behind the door which is 1/2 to 1" farther out from the inside of the wall)