Regarding the XL pads, I just realized I installed seam up. Does it matter? I feel like I pressed my luck regarding potential damage just switching out once and prefer not to reverse the position if there is no need. The thickness seems symmetrical, so I'm thinking the difference is only cosmetic.
I doubt it matters, outside of it being a pain to get them on upside down. There's a little flat spot on the plastic shell of the pad (on the inside), that you have to match up on the bottom of the headphone...so it probably should be the correct way (with the seam down). Otherwise it would just be universal and wouldn't have that indentation.