Over the course of the next 8yrs, the Thundercats would dominate the WOAA. In the 1990/91 newly formed Senior "A" finals, they were challenged by the Tavistock Royals. A hard-fought series ended when Brian Sweeney would score in overtime in the 6th game and allow the Thundercats to emerge victorious and Senior A Champions. Some members of the team took immediate vacations but halfway through they got word that the WOAA had been attempting to contact them to set up dates for a Grand Championship series with the Arthur Tigers, the Intermediate "B" champions. The 3 out of 5 series would go the distance with Arthur pulling off the upset to win the Grand Championship. The series of course was not without controversy. The two head coaches were longtime friends who would test that friendship severely. A questionable arena malfunction canceled game two in Arthur, which resulted in the series lasting an extra weekend longer. This resulted in the Cats losing the services of a couple of players for the last two games, due to prearranged trip commitments to Florida. Arthur would win game 5 in Durham in front the largest crowd ever (1,000+) people, to claim their only Sr. A Grand Championship.