Help with a good vertical stabilizing system for quadrotors?

I've been working on a stable quad rotor with good lifting capabilities, but my aircraft struggle with being vertically stable making airdropping things a complete pain. They always have the tendency to spin towards one direction (maybe the rotors aren't canceling each other out completely?) Any tips on how to refine and improve the stability of this design?

Here's a picture of my first original quad design, the Skywhale II (attached is a light tank and the .bsg file)



I need also help on making a self stabilizing quad.

Also i've seen the skywhale, and it don't have auto hovering, so its very bad at flying

Also, Why my Picture is White?
There isn't collective pitch on eternal wars sky crane, I put a tilting mechanism on mine to help with lifting, so the body could be at odd angles in order to carry uneven weights, it isn't necessary tho. The spinning vertical propellers stabilise the machine, having 8 contra rotating rotors works better than 4, I made one with 4 and it is less stable. I'd go with 8 if you want more stability.
Collective pitch is difficult to achieve with these builds as they have 8 rotors, with many blades, having collective pitch would drastically increase block count and would be very complex, reactions wheels work fine.
@wasdlucas, i think the picture needs to be 200x200. Also same for you, have a look at eternalwar's skycrane, should give you a good starting point.