I watched a noted gunsmith reassemble one of my Smiths using a "pin punch" exactly sized to the screw hole (4/40)on bottom of the top lever. After tightening the screws and creating a bit of a press fit he inserted the punch into the hole and while the action was held firmly in a vice he used a small hardwood V block to carefully push the bottom of the top lever into the slot. When the hole didn't stay in it's mating position he tightened the mating screws just a bit until it did. After it was seated he tightened the action a bit which kept the top lever in position. Remove the punch, insert screw and tighten. He made it look reasonably simple when you have the right tools. Proper punch and his "secret weapon" which was the V block. But he's the gunsmith and I was the spectator.