Fourteen to twenty, and why the range is honest
The published figure is 14 to 20 passengers depending on the model, and the range is real rather than cautious - there is more than one H2 build and they do not all seat the same number. That is why the useful thing to send is your actual travelling count rather than a rough one. A group of sixteen fits comfortably in some builds and is tight in others, and reservations would rather confirm the right car for your date than have you arrive and do the maths in the street.
It is built to be the venue, not the transport
TV screens, surround sound and full party lighting, and karaoke is worth asking about when you request the quote. This is the vehicle that gets booked for bachelor and bachelorette parties and for birthdays where nobody particularly wants to end up at a club - the point is the three hours in the car with your own music. Continuous hourly service is the right shape for that, with a three-hour minimum Monday to Thursday, and it removes the risk of standing outside somewhere waiting for a car to come back.
Stops, timing and the end of the night
Nights like this run long more often than they run short. Give a realistic end time when you book rather than an optimistic one, and list the stops in order, because a route with four stops across the county prices differently from a loop around one town. If the night finishes somewhere other than where it started - over the grade, or down in the basin - say so at the booking stage. The return leg is the part that changes the quote, and it is much easier to agree in advance than at one in the morning.