At beginning I thought that rear dropouts will be made of aluminum. Finally, I ended with dropouts from steel. I modified steel connector, thickness of 5.4 mm.
First, I drew the shape of the dropout. I used angle of that of the old steel bike. I utilized hole (10mm) and made the think easier to cut.
I cut dropouts from the connector with manual abrasive cutter and saw, gradually. To adjust the shape of both dropouts equally, I used clamps and rasp.
Right sided dropout was adjusted according to shape of rear derailleur hanger. I drilled couple of holes into dropouts to make them lighter. Weight of the dropout without holes was 70g; with holes 61g. Whether it was of any sense is questionable.
To prevent galvanic corrosion, dropout was insulated by glass fabric. On the right, final dropout with glass fabric applied, on the left, one side with overhanging glass fabric. Overhanging fabric was bended and glued to dropout with cyanoacrylate glue. Excessing glass fabric was cut out by cutting knife.