Just got certified as a new S40 owner! Now looking to customize just a bit with a single seat, and maybe a different, simple rear fender. See attachment for an example of pretty slick bike that gave me inspiration (maybe someone's out there???). So now what? Anyone know where to get the necc. parts to fit this bike w/o redoing frame, etc.  Any recommendation re seats?  Is this a job I can do (very rudimentary skilll level here) or would I need a custom shop?  If the latter, anyone have leads in SoCal? Any thoughts appreciated. Many thx.

That is THE nicest invitation to 'Sit on it" I've seen.

It is all a matter of making the bike as comfortable as possible.  IMHO this is a safety issue -- being comfortable on the bike allows you to concentrate more on the traffic around you.

The stock seat is a compromise to fit a mythical average person.  By playing around on the seat mounting you can adjust it to a more perfect fit.    My seat, sprung rear and front pivot at 1.75" is near perfect for me.  Sluggo, a little shorter than I, has his rear fixed a little lower than mine, with a bouncy front.  (talking about the seat on the bike!)