Still working on an old 93 Mauser, I'm on my seventh stock. Picked up an original with a few cracks, mainly inside the back of the action area. They're thin "hairline" sized cracks. What's the best filler?? I do not think they're wide enough to glue, I'm thinking putty or Minwax filler (may match wood) or what about acraglass, bondo, etc?