Sorry Apkley it took so long to ans your question. Like I said I used cardboard from the shipment packing to make a prototype and made sure it fit so as not to deal with fitting a glued up insert. I found a supplier to purchase some extra okoume plywood. The trim around the openings are water oak as is the molding below them. Those rings were cut out of a single board and then routed to fit as well as rounded off. I made a form to shape them to fit the curve and sandwiched them in it one at a time after steaming them, just used a dutchoven with a small colander under the wood to keep it out of the boiling water for about 10 min. You should make the form have a slightly sharper than you need curve to allow for some spring back. The molding was also steam bent but in a 4” pvc pipe connected to a teakettle spout. Just make sure to quickly apply the shape desearded shape as all ability to maintain shaping leaves quickly as it cools and ware gloves. The curve for the cabinet is easy as the plywood bends easily and stitch and glue works well there, 1/4” thickness is more than strong enough and once epoxy and some fiberglass is added to some inside corners it all becomes very rigged just make sure you work on a large flat surface to prevent any warp once finished. I think I used 4 nuts and bolts to fasten it to the bulkhead and this allows me to remove it if needed in the future. Good luck.
Bill