I hope everyone already knew this... So a better way when you are by the weap factory go behind the tibrefinery you lose with your stealth like 50 health. And only begin shootin when your behind the refinery. Cause most of the times when i did this nobody saw me and i destroyed the powerplant with one stealth tank. Don't shoot to high so they can't see the explosions.
The best way to do this is when your base is under attack so there aren't many enemy in their base.
And don't shoot people when your heading to the enemybase if you do this tactic. That people could have destroyed you. This worked many times with me...