I'm in the process of gutting an 1882 Italianate with balloon construction. The exterior walls are 2x4 with 1" x 12" horizontal planking under the lath and plaster on the interior. I plan on using foam insulation, most likely Icynene. Still learning the open cell vs closed cell debate. Anyhow, it seems such a waste to remove the 1x12 planking it's so solid. Should I or can I leave it up and have the foam blown in behind it? I like the idea of an extra solid wall behind the sheetrock. The other option would be to remove the planks and scab onto the 2x4 making up for the lost bulk of plaster & planking and inturn get a thicker wall of blown in foam, (5 3/8") under the sheetrock. What to do? Thanks.