I have heard that with coilovers, where the shock bolts into the rear turrets, they ought to be seam welded and strengthened as that section is apparently only spot welded. Obviously with the old setup, the spring was supporting the weight of the car via the rear chassis legs and the shock doesn't place a lot of stress on the turrets.

If the spring is acting on the turret, it will be the turret that is supporting the weight of the car which it wasn't designed for. I don't know how strong the standard turrets are at the back but I know I will be strengthening mine as a precaution as I can't be dealing with the hassle if my turrets crack and fuck up! Prevention is better than cure as they say!!