As others have said - 4 hours is plenty of time for the Fcl lounge. 1 hour for drinks, one hour for massage, another hour for drinks and food... and you still have plenty of time up your sleeve for shopping or duty free.

I've had involuntary layovers of 6-7 hours - pretty much climbing the walls by the end of it. If the layover had been close to/over 8 hours I'd have gone to a hotel.

Fcl isn't sold on domestic flights, but the seating is available to business class passengers. So the 747 might be a good choice for you.

Tip: manage your expectations on the lounge massage. You'll find much better ones at just about any reputable massage place outside. They can vary in quality in the lounge - to the point where they can be less than enjoyable (think stuck under the A/C flow, cold, with sticky drying oil).