Thinsulate is an excellent case foam alternative. It is an effective lightweight acoustic dampener that is extremely versatile due to its wide compression range, making it usable for virtually all keyboards.
Dimensions : 500mm x 120mm
Thickness when fully compressed: 1mm
Thickness when uncompressed: approximately 13mm
You will need to trim Thinsulate to your case internal dimensions.
You will need to compress the Thinsulate as you are assembling your board together.
Thinsulate may fray. Use with care! Not recommended as plate-PCB foam.