[lovedebbii]

I'm totally willing to give a 30D/30DD a try (except that I don't remember ever seeing that size in a store, so I don't know if I can actually find one to try on, maybe I'll have better luck finding a 32C) but somehow the principle of the sizing method still doesn't make sense...shouldn't a D cup be larger than a B cup, regardless of the band size? The explanation that a 34B = 30D is causing some cognitive dissonance.

Thanks for the feedback!

Think of it this way:
34 band and 36 bust measurement equals 34B
30 band and 34 bust measurement equals 30D
The ratio of band to bust is bigger on the 30D but the 34B has a bigger bust measurement.

The idea of a sister size is that the two volumes equal each other. So a 30D would be able to fit into 34B because it's the same cup volume on a smaller band.

There are fit issues with sister sizing as you can see because the 34B is made for someone with overall bigger measurements.