Assuming the spigot in the centre of the hub is engaged in the wheel, two bolts will hold it quite safely as long as your not going to be driving like an idiot. You have to remember that the wheel bolts are specced to deal with braking from top speed which is by far the worst load case scenario. The spigot and bolts support the vertical loads from the weight of the car in shear (strong), the tensile strength of the bolts supports the cornering forces (not quite so strong but still strong) and the shear strangth of the bolts supports the loads imposed by acceleration and this will be the weakest load case. Drive carefully and it will be fine (leave plenty of distance in front of you just in case!).