A Vaughn ( spelling? ) California Framer, with hickory handle, is THE framing hammer, and I never want to hear about Estwing steel-shaft hammers again.
The shock-absorption in the hickory is wonderful.
( I've never worked as a framer, but I have worked a few years as the grunt-guy on construction sites, and have tried many different tools, trying to find the ones that work properly for years )
The only question is whether the springiness of hickory would make it prone to falling-off the file quicker than rock-maple would..
Mind you, humidity expansion/contraction would probably be a factor in that, so maybe sealing the stuff, soaking it in varnish or something?
Anyways, it's an experiment I'd do, and if the hickory doesn't work-out, then try rock maple, see?