The Ju87-G with the 3.7cm cannons was difficult in real life, as in IL-2 GB, to be very effective with. You must be precise with your shots, because you have so few rounds of ammo. In the game this means getting your joystick tuned properly to not cause overcorrections as you make your gun run. You also need to be very patient to set up for the proper attack approaches. Hitting the sides and rear upper decks is the best way to destroy tanks, but requires a climb and short dive for each attack. Not a huge problem when there are no enemy fighters, but if there are.... If you still enjoy IL-2 GB, you might find that using the German air-burst bombs are very effective against armor. Use the AB250s (they are the ones intended for anti-armor) and learn how to set the fuze to detonate a second or two before they would otherwise hit the ground. You will need to learn how to use the Stuka's bomb release altimeter to make sure you have dropped at the proper altitude to give the AB250 enough time to fall yet still detonate above your target. Because it is a cluster bomb you can sometimes take out multiple tanks if they are closely packed.
