I have not seen a quad on the 2.4's but have seen them on the 3.2's. I am 100% in favour of a full custom system for the 2.4 to help her breathe, but, from a personal perspective, I find the quad exit a little strange looking on the car. I am not 100% sure why, but for some reason the rear end doesn't suit 4 pipes? sounds strange I know, and its a personal point, but a pair of larger ovals or round exits looks way better. My personal preference for a full system (on the todo list) would be straight through, turbo back system finished with 2 x 120X80 ovals, slash cut to the contours of the rear. They would still fit in the original exit holes in the skits and stay in keeping with the lines of the rear. As I have said a couple of times, its a personal thing, and your choice of quads is as valid as my choice of ovals, so if you think it will look good to you, go for it
One point of note about longlife though.... They operate a franchised system where anyone can become a dealer / fitter. My closest fitter is Peterborough, and is actually an ICE installer, that has branched out, so the fitters have no real exhaust experience or training and in general the company has a bad rep, so there is no way on earth I would ever let them near my exhaust. What I am saying is, check the reputation of your chosen branch, as everyone is different.
Another potential option for you to consider (one I am also considering) is, assuming you already have a DPF bypass pipe installed, just buy a CAT bypass from Alfatune, then choose a set of sport back boxes from Novitec, Ragazon or other reputable manufacturer. You will get the same end result using known reputable parts. Ultimately the only things slowing down the escape of gas are the CAT, DPF & flow in the backboxes, as Longlife would not massively or noticeably increase the diameter of the pipework under the car as its already quite big on the 2.4.
food for thought...