Re: Researching spinnakers
You can definitely use a symmetrical while sailing solo. Ask anybody who's been in a solo race. While it's a thousand times harder without an autopilot, the OP did say that he already sails solo, so there's a decent chance he already has an autopilot. I couldn't recommend spending much time going up on deck without one.
Most of the time we used our symmetrical spinnaker, it was double-handed work, with my wife steering and managing the mainsheet. This was very manageable as we only used the sail in conditions where we thought it would be easy to use.
Regardless of which type of spinnaker you choose, including no spinnaker at all, there are risks that are exacerbated for singlehanders and mitigated by autopilots and crew. I would never plan a sailing trip based on the assumption that nobody will ever need to go to the foredeck, a place where so many essential boathandling activities occur. So saying, "You can use this sail solo without an autopilot" sounds like asking for trouble.
If he doesn't have an autopilot, why look, another Christmas idea...
1972 Catalina 27