The main bore in the smaller AP props is 1/4", 0.250. Trying to push a 0.280 shaft through it will require a strong arbor press. That is a 0.030" press and there is no way to push 7mm shaft through it with out damage to the shaft and absolutely the prop. There are no tapered holes in a new prop, There may be stepped ones, but not tapered.

The prop reamers are the only way to go.Assuming that the center hole is straight to the back of the prop, the reamer will keep the hole centered and square. Iuse a drill press and lock the prop down to the platform and ream it. Be very careful that the prop can't spin. Hand reaming is best done from the back of the prop. After the right size has cleared the prop, I then continue to the next size to clean the edge of the hole, Just enough to clear the burs out. Do this from both sides. If you don't, the cones in your porp balancer will not center properly in the hole.

Don