Hi David,
your history isn't too bad, but a few corrections for the sake of accuracy. The first FAI turnaround WC was in 1985. Hanno flew an ST 61K in 1987 and used the prototype Hanno special in 1989. The first notable appearance of a 4-stroke 120 was in 1987 when Naruke introduced his Silent design powered with the first version of the YS 120 4stroke. The OS 120SP (supercharged) that Hanno used in 1991 was notoriously cantankerous and had a nasty habit of violently backfiring especially if it was just a tiny bit too lean. The WC wasn't won with the clearly more powerful 4-stroke until 1995. I believe (ok, too lazy to check) the YS 4-strokes have won every WC since (mostly due to CPLR's regular appearance in the winner's circle).