My last notes from the last draft:
The shot that does damage through the armor does both SI damage to the frame *and* one internal damage hit.
Internal components have effectivly one hit, regardless of SI damage. If you feel this is unrealistic and don't mind the additional calculation work, use the same SI damage chart in the Vehicle design chapter as the vehicle .
My suggestion was to crib from the old Car Wars rules. Calculate the SI values of all the components, and draw a small crude picture of the vehicle with a basic layout of the components. Each time a shot goes through the armor, you can draw a line through various components, each of which takes damage.