I would think that a .0002-.0005 interference fit would work just fine.
Your issue may come in actually achieving that tolerance with a reamer. At .0002 tolerance you're looking at a ton of factors that will influence your final size. Reamer length, initial hole diameter, spindle/chuck runout, tailstock misalignment, toolholder type, lubrication type, speeds, feeds, etc can all make or break you. Honing or boring would work best, but aren't really practical for FRC use.
You can find some good information
here about choosing the right reamer and pilot drill size. The minimum tolerance they recommend is .0005.
Your best bet may be to try to ream a few sample holes in steel just to see what you need to do get the right sized hole in there, without ruining gears.