I have a British issue firesteel, a U.S. issue aviation fire starter, wads of tinder, and some lifeboat matches. I can also put some lead sinkers, hooks and line, potable aqua tablets, stainless wire, or whatever else fits. The handle of my Crain Life Support Systen 2 is pretty large, much larger than a Chris Reeve handle, so I can fit alot.
Jack Crain's Life Support System of hollow handled knives have never had a broken blade. It's reportedly been used to cut a 55 gallon drum in half by being beaten with a baton, no loosening, no breaking. More than anyone would actually need a knife to do.I have complete faith in the stength of these (Jack Crain's)knives. Most people were put off of hollow handled knives because of the huge influx of cheap Asian imports, which were never intended for actual use and were dangerous to use. Robert Parrish also used to make a fantastic hollow handled knife.
With my Chris Reeve Shadow 4, I cut the flint rod out of a "Blast Match", the big 3/8" diameter size, and epoxied it into the buttcap. That way it's always there, and the knurled butt cap makes a great slip free handle too. There's enough room at the bottom of the handle for some tinder as well.