Dave - I used to use one of these benchtop shears that had an identical shearing motion except it was hydraulic-powered (i'm assuming you're referring to one like #130-5705). With the stock only being 0.5" wide, you might be OK, but I found that they do tend to cause the piece to twist. You could probably hold ten-thou tolerance with a stop-gauge. A much more accurate, square & repeatable method would be with a flat-shear (i've got a 12" Diacro. Repeatable to much tighter tolerances. Limited to 16-gauge CRS, but there's a chance the fact that this is only 0.5" wide might be OK...
Tormach PCNC 1100, SprutCAM, Alibre CAD