At 100% the handle is 105mm long (total). The hole is quite small (3mm) but you can either re-drill it or warm the file when you push it in.
I added micro-cuts around the holes to trick the slicer into printing extra material around the hole so you have some beefy material to hold the file's shank.
The design is inspired from a screwdriver handle I have and that I find good.
You can always print bigger or smaller to accommodate any files or hands.
I provide my original SolidWorks 2014 files so you can modify at will
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