Need help designing keyway in gear

[sanddrag]

Will the oversize (1/8") keyway in the picture below be okay to make? I want to go oversize because I'm worried that a 3/32 key is too small for where this gear is in our box. It needs to be able to handle some torque, maybe somewhere around 13 Newton-meters. But in the same way I'm worried that 3/32 keyway is too small, I'm worried that 1/8" is to large and does not give us enough "wall" between the top of the keyway and the dedendum. This gear is Small Parts number gss-2014 and is getting bored out to .375 Although we would like to, design contraints keep us from moving to a bigger gear.

So, the question is, 1/8" keyway and thin wall, or 3/32 keyway and thicker wall?

Or would cross drilling through the gear hub and shaft and pinning it be better? If so what size pin? Should we key AND pin?

EDIT: One more idea, maybe go with the 1/8" key but set it a little deeper in the shaft and don't cut the keyway so deep in the gear, but I believe it gets broached once without a shim and then again with the shim. Would anyone know the size of this shim?

EDIT2: I found this very good pdf document but I do not know how to do the calculations myself. Hopefully someone can give me a definite answer and reason of how to make this gear reliably spin with the shaft, at the torque around the number listed above.

Here's the pic: