I previously had a GG/H cup but following my double mastectomy and reconstruction, while the aim was to get me to a B/C cup, my right breast is significantly larger...... I used a soft form support bra initially following my second mastectomy and reconstruction of both (via a DIEP), however it did not provide the support I needed.
Months later (following complications - long story), I went to "Leila O'Toole" in Sydney CBD and purchased a post-surgery mastectomy bra. This helped with the support and the compression and was fitted expertly there.
The bra I have are "Anita - Lisa". It has space for prosthesis inserts to go, even those I don't specifically need that component, while keeping the bra in place and applying light compression. (Medicare provides a reimbursement of up to $400 per breast for a prothesis, if indeed one is required, and these can also be purchased here and used within the specialist bras.) I also purchased lymph drainage pads from them. It took me a long time to find a suitable underwear provider in the weeks and months following my surgeries and I'm so glad I eventually came across them. Worth the visit.