For those that do their own fireproofing be it for money saving or to have more interior room inside your safe. How did you do it? I read that most use layers of sheetrock around the safe but some say you need a gap between the safe and the sheetrock (6 inches?). What is the purpose of this? Seems like this space would just allow the heat to get into the gap and make the fireproofing less effective. Would putting multible layers right against the safe be bad?