I am also looking for inputs on HAPI or GPI if used commercialy. Ihave personally used GPIs on Naval ships and found them quite useful. Having flown without them earlier when used them later found it to be pretty useful. However on fixed platforms how to align for prevalent winds. One of the inputs I got was that they had used the system in North Sea fitted on rails around the perephery of the deck.
Any corroborations or inputs