How to penetrate StuG III G weak spots - World Of tanks

World Of Tanks - armor test.
Tank: StuG III G
Type: Tank Destroyer
Tier: V
Country: Germany
Game patch 1.3.0 (test)
Used:
Pz. III E 50 mm Caliber / 60 mm Penetration (AP)
M5A1 Stuart 47 mm Caliber / 81 mm Penetration (AP)
Crusader 57 mm Caliber / 110 mm Penetration (AP)