Both boards are mechmini2’s with lubed retooled blacks (and 63.5g sprit springs) - lubed with 104 and 106 as always.
Here’s the test:
The cyan contains a fixed layout aluminium plate, the purple a fixed layout steel plate. Both 1.5mm.
The sound is relatively evident - on the feel the steel is more rigid, and has less variance in flex across the plate.
If anyone was expecting to hear to telltale ping of steel I did some testing there with existing boards and it’s notable primarily in low profile trays. The combination of high profile (in this case in small part the polycarb base on the board) and top mount does an admirable job of removing it.
I wanted to show the sound at it’s best. In my experience a lot write off steel immediately thanks to a perception of ping.
Also - I conducted this test with PBT dye-sub DSA on both (previous tests done with one of each as was noticed by @holtenc) to eliminate that as a differentiator.