I'm curious has anyone ever been able to effectively use a Dson character (like G1, G2, G3 or G8) in Poser's Bullet Physics engine with soft body dynamics?

It appears to have never worked for me. Maybe I'm doing something wrong.. My program always crashes. Anyone?

(It be cool to get a picture or video demonstration)

If you maintain the character's DSON subdivision then definitely the program will slow down and crash.  Other than that, I haven't seen any threads addressing any of those figures with Bullet Physics.

I'm just curious has anyone done it or can it be done?

I'm desperate to know.

I don't think I've ever seen any successful "jiggle physics" done with bullet in Poser, if that's your goal. I might be wrong though. That kind of thing is best handled by body handles or morph sets, IMO morphs are still the best option for that. There are, however a couple/few figures with relevant handles that work pretty well for that, if supplemented by JCMs that correct certain shortcomings. A morph set for breast physics, uncompressed, might look something like this...