Give the SM +4 giant a lifting ST of 110 (or more). Then change the scaling of armor and weapons to:
- Multiply cost and weight by (height/2 yards)^3.
- Multiply DR by (height/2 yards).
That means the suit of plate for a SM+4 (10 yard) giant is 125x weight/cost, but at least it has DR 30, which is respectably effective against a 9d swing.