I was told by a company that, they put up thin flat insulation, foam board that is breathable, and put the siding over that. This is now essentially a flat surface and gives you extra insulation. It needs to be breathable so you dont cause condensation. Does roofing felt breathe? I would check on that. Make sure you dont drive the nails flush, the nails should not be driven all the way because the siding needs to be able to expand and contract depending upon the weather. It will buckle if you nail it tightly.