And from a recent PM discussion I had with a DDFer, whose LOR was a bit at sea:
It's critical to talk to someone who knows the subject intimately, it's all too easy just to say "no".
Tell him to check שבט הלוי ח"ג סי' כ"ח וח"ו סי' ל"ד, where he paskens to keep d'oreisas on the safek day, which is Friday in Hawaii.
There's also a good discussion in שו"ת נשמת שבת ח"ז סימן תקכ"ז - same psak. See also the simanim a bit before and after, he discusses all these shailos at length.