Actually, a 150T with its 24" depth would be an awesome lionfish footprint. IMHO/IME, the major issue with sedentary lions is often the fact that a full-grown P. volitans has a hard time turning around in most setups, so they sit there.
We keep our 12" volitans in a 100 gal "wide" (48" x 24" x 20"), and it spends most of its time gracefully cruising the tank as opposed to sitting around. You'd be surprised at how fast a big lion can be when it has room to "run" if you ever have to catch it! I just love the way it perks up when one of us enters the room, doing its best to get a treat.
That being said, once we knock off a couple of pending projects, we hope to move the volitans to an even larger setup (300 gals or so).