I have been building a 250 gallon RF smoker the past few weeks and have almost everything ironed out except the vent for my firebox. Since my fire box is a 30” dia 1/2”thick pipe 32” long I can’t easily put vents on side of pipe leaving all vents to the door side. According to calculation I need 65 sq inches of vent and would like to make it on a slide but need it to fit on the door(I think). Seen several ways people have done them but surprised I haven’t seen more for 250 gallon propane tanks. I’m afraid I can’t fit a horizontal slide in the space I have and still keep everything solid. I want the door to go to bottom of firebox for easy clean out with a half moon shaped scraper. Any advice would be appreciated. Have to let air out of tires to get out of garage .