Rigrolled
Hey
It's kind of hard to evaluate the solve as your keyframes are a little jerky 😉 I think the spline interpolation is over shooting, or maybe you just need a few more inbetween poses set.
Can you post what just the bones are doing? I suspect that might be the cause of any unnatural squashing you're seeing. With physical solves you have to be attentive to the physical limits of where the bones could actually go.
When you build attachments, are you selecting a group of vertices one mesh, then shift selecting the second mesh? This will auto paint your map. In the Ziva tools menu there is also select vertices by proximity.
I usually just use binary (0 or 1) values for attachment maps, unless I specifically need some attenuation. I find attenuation helpful when working on the fascia or fat layers.
Hope this helps!
Cheers,
Andy