Tuesday September 30 1997   Table Tennis Big cash bait for Grand Finals   JESSIE HUI Prize money totalling US$210,000, the highest ever, is being offered at the CTS (HK) ITTF Pro-tour Grand Finals, which will be held from December 18 to 21 at the Queen Elizabeth Stadium.   International Table Tennis Federation (ITTF) executive vice-president Yap Yong-yih said hosts Hong Kong would be granted wild cards to the elite events, which will feature top players from this year's 14 international open championships.   The top 16 men's and women's singles players on the ITTF Pro-tour rankings will be eligible to take part in the event, while the men's and women's doubles will feature the top eight pairs.   Kong Linghui , Liu Guoliang , Deng Yaping , Li Ju and Yang Ying, all of China, are expected to participate.   Kong and Deng lifted the men's and women's titles in last year's grand finals in Tianjin.   Yap added next year's Pro-tour would attract even more top players as points would be carried forward to the 2000 Sydney Olympics qualifiers, starting early in 1999.   He also said the ITTF was looking to add the mixed doubles to the Olympics.   He said a research centre had been set up in Canada to experiment on new rules to improve the quality of the game.   "We are testing bigger balls, which help the audience see the ball more clearly on television," said Yap.   "The games will be slowed down a little, but the audience will see more play between the players. The games are too fast at the moment."