need avi help

im trying to make a sash that will extend from arm to arm with physbones but its not behaving right

https://preview.redd.it/qjrymljcnerd1.png?width=1920&format=png&auto=webp&s=b582c0d2a21c35f41a19011da12ef126f96698aa

physbone setup

https://preview.redd.it/libo42bknerd1.png?width=1920&format=png&auto=webp&s=543a2b7e2df3c76b696c1c8d95c226e5e1ba631c

how its behaving

any tips to get this working corectly or if this even posible