if you look around where your rear turret are fitted you'll find that they are spot welded only with the extra force that coilovers put on the rear turret this can cause it crack and or worse still the welds to give way

what some peeps do is seam or stitch weld the rear turret mounts to give them extra strength and thus spread the load that it now subjected to from fitting coilovers also advise a rear strut brace also

hope this helps