From an archived version of the currently inoperable Island Express website (emphasis mine):
How many guests can a helicopter accommodate?
It is determined by total passenger weight. Below are the maximum number of guests for each of the styles of aircraft we fly:
Sikorsky S76 – 9 guests
A-Star – 6 guests
JetRanger – 4 guests
FAQ - IEX Helicopters
That should put that speculation to rest.