both my crossovers are laying in the bottom of my foor wrapped in a plastic bag to protect against moisture and stuffed with some shop rags to help with the vibration of opening and closing the doors , been working fine for 3 years that way , crossovers generally dont produce much heat at all maybe 5 degrees over air temp if at all and i have pioneer 300 watt amps yes plural amps , one bridged per front door , key thing , while you are doing it put some dynamat in and your mid-bass responce in the door is great
