You make me want to have a try now. I think you are right about needing a good file though. The older the better. I believe lots of modern files may just be case hardened.....sure i read that somewhere.With a good file you've got great hard steel, as long as you don't effect the original temper then you don't.
Drilling holes can be a problem, but for the smaller knives I've made in the past I was able to wrap the blade in a wet rag to keep it cool then heat and anneal only the tang with a plumbing torch.