well.. applying spring bones to the secondary arms would have them hang down and move slightly with right tweaks, but they would bend in odd ways.. its how it is with vrm 0 files. only vrm 1 would give you bone constrains that could prevent that and allow upper arms to influence the lower arms
but.. even if the arms just ' wobble' about, they would look more natural, in comparison to stiff arms. you can add a lot of slowness in how they swing, so they don't flutter about like hair
( also what? i could not translate 'bourne' )