im getting ready to install my heater for the winter. Figured I'd takle the sub at the same time since right now, I still have the factory clarion free air. <BR> <BR>Think its possible to fit both? I was maybe thinking of putting the heater core to one side and maybe makeing the sub fire towards the hull of the boat so I could use the space above the heater for the box airspace. <BR> <BR>does a heater need to be mounted horizontally?