Question about radiator box size

Odd question so I'll try to be as clear about it as I can. I am trying to build a box/bench over a radiator and I am wondering if I can make the whole thing one depth which would make the front of the radiator part of the box 12" away from the radiator. Or do I need to make the radiator box front closer to the radiator, there by making the depth different than the rest of the bench unit. I would prefer to keep the same depth across the whole thing so long as it won't cause problems with how it hearts. Thanks!

Sterling