Hi allyshake,
Yes you are right in thinking that the underwire casings on a cradle may give to big a gap between the cups for your friend. First if you have a look at the article on the push-up bra (Cowboy Bra) and think about shortening the centre front “ribbon” between the “on-cup” underwires so that the underwire casing touch each other this may give a part solution.
Next, if you are considering a strapless bra take a look at the article on the “Overwired” Jack Glick strapless bra. Now think about this bra with out the overwireing but with Vertical cup boning to hold the cups up. Another article to look at for vertical cup boning for a strapless bra is the forth bra article on different styles of bra.
So if you combine the overwired bra shaping with the vertical boning half-cup idea you should be looking at a design similar to the attached picture MW85SS.jpg. As you can see the bra in the pic has no underwires just curved vertical boning on the cups (the boning is strait until the bra is on), also notice how “deep” the wings are for support, they are the full depth of the cups.
I hope this helps, I was thinking of doing an article on making a strapless corselet from 1953 that uses a similar cup support idea, see pic bild227.jpg.
And finally, trim stitches? It just means the zig zag stitches that hold on the trim. as you sew on the trim over the panel seam do not “stray” off the trim and stitch on the Powernet alone as when the garment is put on the elastic “pull” on the stitches will pull small holes in the Powernet weave. Powernet must have a second layer to take stitching. It’s all to do with “stress points”.
Corset Hugs
Mark.

Thanks Mark I will work on some design ideas and post them once I have figured out the best approach. I have posted (here) the original question to give your post some context for other members. regards

Kissing Breasts

I am trying to make a bra for a 34D+, young woman who has only 5mm between the breasts at the BP level. She loves her natural cleavage and even with D+ cup can get away without a bra. The bras she does wear however are too small in the wing and cup but she likes the way this pushes her bust up even more than it naturally sits. My problem is how to make a cradle with such a small gap available. Here is some advice I have found www.herroom.com/breast-separation,333,30.html. I want to use a full/strapless style for her bra. Does this mean I need an underwire or should I work through a 'soft' design? With a wire style there is a minimum of about 2.4-3.2cm to allow for encased wire to fit when sewn in. It seams that a soft style may allow for a much narrower cradle but will it give sufficient support for a D+ cup sized breast? Can you see my dilemma? In the Grading 1 article you mention that the width of the cradle at CF should not change when grading up but can I narrow it?