Bamboo and Exotic Wood Floors - Levelling floor for bamboo t&g

and by that I mean flattening. The subfloor has one major dip ~1/4" and a few smaller ones. The subfloor is composed of abused, ancient t&g planks laid perpendicular to the joists a couple have cracked at the ends, but there is very little movement. I've read about many different methods of levelling the floor, levelling compound, plywood, grinding... I think the one that seems to make the most sense is to layer strips of roofing felt to fill in the dips. Has anyone done this before? I'm planning on nailing the t&g down.