I FINALLY GOT THE FIREBOX OPENING CUT IN MY TANK. I USED A LASER LEVEL TO GET THE CUT STRAIT. I THINK THAT THE OPENING IS ABOUT THE RIGHT SIZE BUT I AM STILL A BIT CONFUSED ON HOW TO FIGURE THE AREA OF THE OPENING. I NEED TO GET THE INSULATION AND OUTSIDE SKIN PUT ON THE FIREBOX AND VERTICAL COOK CHAMBER SO THAT I CAN FIT IT TO THE TANK. I AM ORDERING THE CERAMIC BLANKET INSULATION 2IN THICK, RATED AT 2300 DEGREES MAX. IT IS 8 LB/FT3 DENSITY. I HOPE THAT THIS STUFF WILL WORK. HERE ARE A FEW PICS OF WHAT LITTLE PROGRESS I HAVE BEEN ABLE TO MAKE THIS WEEK.