Sai Kung town is horrible on weekends but normally I'll park at Centro, and then walk into town. If I'm under 2 hours it's free for buying $X at the fusion in Centro. It's the best I can find in Sai Kung without dealing with the main town area. If I really have to park in town I usually head straight for the Wilson parking across from McDonalds. They're tiny spots but there's always room and sometimes convenience trumps the parking price, especially if I'm buying something big or heavy.
Quite amusing seeing a police van come to town, 6-8 of them bail out and fan out to ticket cars. If they were more diligent they could easily fund the Sai Kung police running costs from illegal parking alone. They need to be more ruthless in SK, the parking situation is mental.