I dont do any fishing for black bream so can't comment on the areas down south - but I only use a very short leader when casting at or around structure. Basically just the length of my drop from rod tip to lure when casting. I find this improves accuracy on the cast you can also fish a heavier leader with less affect to your lure. When fishing an OSP Bent minnow 86 for bass around hey snags I fish 14lb -20lb leader and only about a foot and a half of leader. In similar structure when targeting bream i use the same length but bring it back to about 6 or 8lb depending on how aggressively the fish are feeding. I prefer the shorter leader not only for the casting accuracy but also as I want to limit the amount of stretch between me and the fish. When I strike or lean back I want to be moving the fish away from the structure straight away. If you keep a big fish's head aiming your way - he won't be able to get you back into the sticks.
Different scenario when fishing over shallow flats. I will then go to a lighter leader for both species and possibly twice the length of the rod. Big long searching casts are the norm as opposed to short sharp accurate casts. Thats my take on it but - with any type of fishing its personal preference
Regards
Rod