This vehicles collection may also be useful. Includes a treatment of the Apache pretty similar to what I came up with, though I wonder about the basis for the DR stats—I can believe DR 30 for key areas but DR 15 all-around seems like a lot for an aircraft. Maybe more knowledgeable people than I can defend it?
The same PDF also has stats for the M230. Includes proposed handling of HEDP ammo, as well as alternate "API" (armor-piercing incendiary). The damage on the latter seems low—no better than .50 caliber weapons. Maybe someone else can defend it though?