Some spillage on bottom/middle edges of inner cup, but fits top quite well. Might be a different story if the straps/band adjusted tight enough, right now it is quite loose. Center gore rests on breast tissue. Possible spillage on outer side but not much. Comfortable to wear but does not provide support.
I have several Thirdlove 24/7 classic T-shirt Bras in my ordinary size 30DD (that's 30E in Thirdlove's sizing cuz they use Euro sizing). I love their Naked 1 shade because it's a nude that actually matches my ghost pale vampire skin (I'm crazy pale) and when I saw a NWT 34C, which should be my sister size in a 34 band, pop up on postmark for a bargain price, I thought it would be a perfect a candidate for a band alteration. I was very (unpleasantly) surprised to find that while the underwires were the same size as my 30Es from thirdlove, my new bra's cups were smaller with a lot less coverage. Thirdlove apparently uses slightly more fabric and slightly shorter straps on their size D and aboves, but I wish I'd know this before ordering a sister size for my adventures in bra altering.