Just make a template of that giant hole, cut it out on a piece of 1/8” expanded pvc, damp the inside with some RESONIX cld squares,screw it to the door and try to use that bar in the middle as a support also then damp the outside and cover that up with RESONIX 1/2” ultra soft ccf. Next you have to make your own fast ring from 3/4” hard ccf, then finally damp the door panels with cld, wrap all clips with tesa tape at the base where the panel meets the door, put the panels back on and enjoy some super dead doors. Its very time consuming but is totally worth it.