I've got about 600+ SFB minis painted and based so far.
I use a variety of means to increase stability.
For DNs and BBs I like to use the
B10 heavy metal base. Being solid metal, it helps with the stability.
And Like Burt, I have shortened the stands on some of my other large minis. This serves a two-fold purpose.. it increases the stability and it gives a nice effect on the table when the minis are at two or three different elevations.
I also weight nearly every base. Once the upright has been glued into place, I fill the cavity underneath the base with plaster and then slap a ex shaped piece of felt over it. This stabilizes the mini and the felt helps to prevent scratches on the maps.