Okay, thanks.

These vessels are not symmetic, and the pressures involved are… not low… so the resultant unbalanced nodal forces tend to be quite wild. I need “strong springs”… Will definitely try that reaction probe thing, thanks!

My solution so far is to add features where I can put restraints, I just would prefer not to because they inevitably add quirks.

Another solution would be to use a wossname explicit transient analysis and set the density to “Neutron Star” and let it just fly, I suppose.