You are correct, you have too many mast base plates. One has a hinge hole but the one in your mast doesn't, so here's what you can do: Drill out the rivets holding on the mast base, get some new rivets, slide the hinged mast base into the mast after you take out the old one, re-rivet that base to the mast, then step it. OR...don't remove your mast base, but undo the hinged plate, save it for another day. Then get someone big and strong to hold the base of your mast in place on the half ball, while you walk the mast up into possition. You don't want to be doing this on a regular basis, it can get ugly if the guy holding the mast base slips! Better to have a couple guys helping you. But if you are going to be taking the mast down often, you are better off to replace the step it has with the one with the hinge.