Per128, Poopinmymouth, Skanker: Would you care to check that out and tell me your thoughts?
The low-poly mesh is both inside and outside the high-detail model, and the resulting normal-map seems perfectly fine...
Per: I cannot see why you say Max7's normal-mapper is "totally unusable"! From what I've tried, it gives equal or better quality, more consistent results than either ORB or Melody, without any raycasting problems regardless of whether the highpoly mesh is inside or outside the lowpoly mesh...
Can you describe an instance (or even better, send me a file!) where Max7's normal mapper would not create a usable normal-map?