Unless the sailing instructions specifies otherwise,
32.2 If the race committee signals a shortened course (displays flag S with two sounds), the finishing line shall be,
(a) at a rounding mark, between the mark and a staff displaying flag S;
(b) at a line boats are required to cross at the end of each lap, that line;
(c) at a gate, between the gate marks.
The shortened course shall be signalled before the first boat crosses the finishing line.
32.2(a) applies. Finish line is between the "S" flag and the mark, no matter which side the RC sets up on. "J-hook" finishes are not required (ISAF Case 45).
Sound signals at the finish line are a courtesy, not a requirement - in other words, they mean nothing - and the absence of them means nothing.
