|I'm new to making FBAs, as my current body bears no similarity to the one I had at 35! A few months ago I made a Vogue pattern that had no darts and needed an FBA. It occurred to me that I could use the technique from a similar style "Custom Fit" Vogue pattern, 8616, to provide the FBA for the D cup I needed. V8616 uses gathering under the bust for the selected cup size, A through D. The pattern I made, V7799 (still available as out of print), fit me really well.
I compared the gathering placement of V8616 to another pattern's dart placement that I know fits my bust well. This required lowering the gathering area on V8616 by one inch on both the front and back pattern pieces, as the front gathering must match the back gathering symbols. I simply cut out the gathering markings for each piece and taped them one inch below the underarm, then filled in the gap I had created with pattern paper and trued the seam and sewing lines.
Make sure that the front and back pieces will be the same length once the front is gathered and matched to the gathering placement dots on the back.
Both Vogue and Simplicity now offer patterns with cup sizes (long overdue!), so both SBAs and FBAs aren't required in these patterns.