Thanks for all the responses! I should've clarified, but I actually meant the Aluminum hockey puck case haha. It has a foam insert on top that the faux leather one doesn't have. I think it would be really sweet to have around, as I worry about squishing the less-rigid cases.
Those frequencies ranges are more difficult to target with tips just because they're in the middle. Maybe give EQ a shot? The upper-midrange dip (to my ears) is partly responsible for the vocal diffusal and soundstage depth; in tandem with the mid-treble dip, it's what gives the U12t a more laidback tonality. That said, the U12t has a very unique type of stick impact as the treble spikes again much higher whereas most other IEMs are leveling off at that point. It sounds like you might be looking for a neutral-bright tuning instead...maybe Diffuse Field like? The U12t is much more of a U-shape.

Tip rolling really is helpful. I tried foam tips once and it was almost unbearably bassy lol. What tips do you recommend to bring out the upper-mids/mid-treble a bit while toning down the mid-bass a bit? I appreciate the help!
Those frequencies ranges are more difficult to target with tips just because they're in the middle. Maybe give EQ a shot? The upper-midrange dip (to my ears) is partly responsible for the vocal diffusal and soundstage depth; in tandem with the mid-treble dip, it's what gives the U12t a more laidback tonality. That said, the U12t has a very unique type of stick impact as the treble spikes again much higher whereas most other IEMs are leveling off at that point. It sounds like you might be looking for a neutral-bright tuning instead...maybe Diffuse Field like? The U12t is much more of a U-shape.