The closest point in the Solomon chain to Timor is about 1100 miles.That's a mightly long way for a PT Boat. To get from the Solomons to Timor you have to pass between Australia and New Guinea--they are only about 35 miles apart. Port Moresby is on New Guinea.
Guadalcanal is the largest of the Solomon Islands and there were only about 24,000 Japanese there when operation commenced in August of 1942.
I think you need to refine the date so that a timeline can be establishedand a more practical identification of the island.