I'm looking to improve ride comfort for my 75 550K and 71-year-old butt and lower back. I've recently replaced fork shocks with progressive suspension springs and rear shocks with Ikons. Now I'm thinking about the seat. The seat pan and foam are original and while foarm has retained its shape, it's probably lost most of its actual cushioning. Question is, what foam to use if I decide to reupholster? I've read about options of closed cell vs open cell a combination or both (closed for the base and open for a softer top layer). Understand gel foam a bad choice and mixed reviews for a top layer of memory foam. And I've found a few DIY videos that are excellent for shaping the foam. Thanks.