The mounting position on the floor is the same as the 4dr, the problem is arising from the fact that in the 2dr, the main hoop follows the B pillar, whereas obviously the 4dr doesn't, and where in the 2dr the B pillar meets the roof, there is extra strengthening that isn't there on the 4dr and thats what's causing the problem.
We can work round it if need be, just need to know 100% that this is definately the correct cage, as there should definately not be this problem.