To be honest, I'm not surprised that your stormboyz are tippy, I'm just impressed you can have them stand at all without the magnets in the earlier pics; some of them look extremely unbalanced. How dense is that green foamy looking stuff compared to the plastic the models are made from? Did you have to weigh down the bases at all?
Also, who's that finecast looking fella to the right of your stormboyz? A 'ard nob you're still working on?