Thanks For the answers...took the flight and had no problem taking roll aboard bags into the cabin, ground crew said plane side service available only if you've tried to put it under the seat and confirmed it won't fit, in which case they will stow it and have it for you at the steps as you leave.

Mistado - JHM is much more convenient than OGG for west Maui hotels like the Westin. If your flight out of HNL to SYD is at 0815 I assume you're on JQ, in which case you will need longer than that to transfer at HNL, not because it's a massively long walK in itself but because -a-the vagaries of JQs interlining might make through checking of luggage a challenge, so you'll have to lug your bags, plus -b- iirc JQ close international checkin 60 min prior to departure which means if the island air flight is on time you'll only have 20 min to collect bags and carry them two terminals over. I wouldn't risk it, not with JQ.