"Service Bulletin SA-003 prohibits aerobatics in Schweizer gliders overriding the POH (answering the question about an SGS-2-32)."

Actually, legally it doesn't. A service bulletin or note or advisory about an aircraft cannot override the approved flight manual or type certificate of an aircraft operated under the aegis of the FAA (Unless it was an alert service bulletin issued in order to get information out quickly while an AD is being processed - it wasn't an alert service bulletin). For it to be legally binding they would have to get an airworthiness directive issued. They did not do this. Not to long ago one of the engine manufacturers tried this sort of tactic and got in a bit of trouble. Whether its a good idea to do aerobatics in a 2-32 being flown in the utility category is a different matter and one I don't have an opinion on seeing as how I've never flown one or worked on one.

You can get a Grob Twin Astir or Twin II for a reasonable amount of money but unless you can find a Twin II Acro which has had the rear fuselage strengthening modification you won't have a glider approved for inverted flight or slow rolls.