Getting the material became the issue for me years ago. One used to be able to buy two-way stretch for light weight girdles, bras or panties, in various colors with elastic and inserts, lace to match. I did this in the 1960-1970s, with patterns from a company (I think was called "Stretch and Sew" that had swimsuit, lingere and basic classic jackets, skirts and outerwear patterns to follow for quality poly blends fabrics. I make a holding pocket in my bras, to insert a washable shoulder pad (right side mastectomy), held in place by snaps for "replacement" of B-C cup which is considerably less expensive than specialty bras. An alternative, assuming you like the fabric at hand to use, is to cut apart a garment that fits from which to draft a pattern. I did this for a lady last year who wanted extra crouch padding, wider waist elastic in cotton-only knit. Does anyone remember real silk in a pongee or a soft crinkled surface? I recall seeing a set of lingere made with that, trimmed beautifully in lace and embroideried flowers.