Having purchased 2 sets of cushions from SBO ( this site) one for our Hunter 25 and then a couple of years later our Hunter 28, I would highly recommend them. Both sets arrived in less than a week and are still in perfect condition.
When we get our next boat we'll order our next set The price is right, the fit is perfect and most importantly, the admiral is happy with a soft place for her tush.
So, here is what I decided. I took out the original cushions and measured the cushion areas. The port side seating has a gap between two of the cushions which is just horrible. So I am going with one long cushion that covers the length of the settee. After measuring, I went to the fabric store and bought foam, upgrading from 3 inch to 4 inch foam. Using my measurements, I cut the foam with an electric knife and put them back in the boat to make sure they fit. They fit perfectly. The admiral picked out some duck canvas outdoor material. We took the foam pieces and the upholstery to a local seamstress shop to have them sew the new upholstery on, with a zipper and piping. I will post pics when complete.
On my 1971 Cal 21 I made a pattern of the area the cushions would occupy (made by taping newspapers together) and took it to the Amish to get made, very reasonable cost and perfect fit (as well as great quality). Granted in Texas there are probably no Amish, but a seamstress or craftsman that works with cloth may be able to come up with something. Best of Luck.