I should make it clear, Rover MG Tomcat :-), although Rover use a washered bolt and studs, flat faced I think.
the centre bore is just there to help you centre the wheel properly, stopping wheel wobble etc. once the bolts are tight there is no movement between wheel and hub due to friction and so sideways load on the wheel bolts at all. think about it this way, all the torque from the engine is going to put a hell of a lot more rotational shear force between hub and wheel than the downwards force from gravity from the weight of the car