West system + filler perhaps to thicken? Aluminium powder, micro-fibre, micro rubber balls?

If I have this right, one advantage of the filler is that it should create multiple impedance boundaries hence reducing the transfer of some of the vibrations.

My initial idea was to cast one or maybe two full faces on the ali profile as a way of creating a reference plane to aid alignment. I've never done this before but working without a reference plane sounds like a bad idea (?)