I think you're correct in thinking that underlining the dress with a batiste might lessen wrinkling. The rigilene boning should be firm enough, but I would also add a waist stay, to keep the waist in place which in turn will keep the top where it's supposed to be.

Thank you for your reply. I will be underlining the dress. I got silk crepe de chine, which is a light fabric, good for a beach wedding, but it will need underlining anyway. I will do a waist stay, I think boning and waist stays are a must with strapless dresses. The dress, which will have a full skirt, should have a nice flowy, drape to the skirt. She has the option of wearing a petticoat if she wants the skirt to stand out more. I know today's wedding gowns usually have a petticoat built into the dress, but I prefer a separate petticoat. That way, you have the choice of how "puffy" you want the dress to look, and also, it reduces the weight and bulk of the dress itself.

And maybe sew that grippy plastic strip to the upper edge to keep it from moving. I use the flat metal bones in the side seams and any darts.

I finished the dress! The plan was to ship it to my son in Houston, then he would deliver it to his fiance when they meet in Hawaii for labor day weekend. (She is currently living overseas) I sent the dress, it made it to Houston but didn't get delivered, due to Harvey. It is at a UPS distribution center somewhere in the Houston area, with no idea when, or if, it will be delivered. For all I know, that dress could be under water now. Doesn't look like my son will be able to get on his flight to Honolulu anyway. I realize that with the horrendous storm, a wedding dress is the least of problems, but it looks like his fiance may have to buy a dress, since the wedding is only 1 month away. Oh well, it could be a lot worse. Fortunately, my son hasn't been flooded out (yet, anyway, the storm rages on) but so many people have lost everything, what a heartbreaking situation for everyone in the Houston area.