I have an old log home place that is great condition. It is roughly 67 feet perimeter and 10 logs high. The logs are dovetailed together. The gap between logs on the walls is roughly 4-6 inches in height. The depth has been dramatically decreased by placing ripped 2x4s in the gap. What would be your recommendation for backing rod for the large area? Could I use fiberglass insulation between the 2×4 and future chinking? Thanks in advance