My 5511 sandcast is mostly original, it had incorrect handlebars and exhaust. I re-installed the original rear rolled rim ( I had to buy another of the po's bikes to get it) I sold a bike to buy a replacement exhaust system, and painted a set of Honda sidecovers so it looks pretty good. I'm trying to not restore anything that's original and usable.
Anyway the question is the seat foam is dry and getting flat, what's best for the bike? Add some new foam to the top of the padding, buy a repro seat for riding and set the slightly flat original on a shelf or buy the Yamiya red seat foam and install it under the original cover? The cover is in good condition and the Avon Skin so soft seems to have given it a new life.
I'm leaning toward the Yamiya foam, that seems to be the best balance between originality and functionality.