should i use the 2x6 cartons or do the 5x6 flat panels work as well?
If you leave the eggs in the carton there will be more mass and it will absorb the sound betterRaw eggs should absorb the sound better than hard boiled.
Remove the shelfSome areas have rules on the situation you haveIt is obvious that your fireplace opening is not deep enough to contain the heat generated while burningYou risk a fire startingI even saw an episode of This Old House, where they failed inspection for the same reason.