Lubing your linear switches with thicker lube, like Krytox 205 grade 0, would definitely mute the clacking. The logic there is that there is now a layer of lube covering your switch sliders and somewhat cushioning them when they hit the top and bottom of your switch housings.
Personally I don't own a aluminium case yet. But the switch plate material should affect the noise as well. If you like a more clacky noise, then using plastic material plates such as polycarbonate plates should increase the sound and maybe affect the pitch. As polycarbonate is a more flexible material compared with metal such as brass, hence more vibration sounds when hit. By the same logic, I believe plastic casings should sound more clacky as well, as the case also vibrates more when hit, compared to metal materials like aluminium.
In summary, if you want more clacky linear bottoming sounds when typing. I would suggest no lube or thinner lube for your switches. (Personally I can no longer tolerate unlubed switches ). Plastic or polycarbonate switch plates. Plastic or frosted acrylic keyboard cases. All these in theory should produce more vibrations when you hit the bottom of your switches, resulting in louder clacks. Try it out and post the results!
