I find that, in general, the taller a tripod AND the lower the center of gravity is the narrower an angle suffices.
When you think about it, the greater the splay angle, the more you are lifting the assembly as it tilts about the line through two feet and the further you have to push it before it overbalances. A taller tripod with a smaller splay angle could have the same sized footprint. It would push over a little easier if the center of gravity were higher, but still would have to be pushed just as far to overbalance.
I've seen others hang weights below their tripods to greatly improve their stability including battery packs to power the mount as well.
One trick I've done on my modified Berry Mount is to screw a pet stake into the ground and to attach it to the tripod with a bungee cord at outreach events. Even the most blundering of visitors won't knock THAT over.