Ok, so I posted a while back about starting my first rf offset, things are progressing well, I just want to check with some gurus about the opening from the fire box to the cook chamber. i still have yet to install the baffle plate but im concerned that the opening i cut may be to big? any thoughts would help. its a 18inch dia tank and im going to cut my baffle plate to 15" putting me 3' below center. thanks in advance.