I have an outdoor shed that was powered with a single 15A circuit by the previous homeowner. I'm trying to rewire it to carry three 20A circuits. It's about a 100' run from my main panel via 1/2" schedule 40 PVC. I would like to run (7) #12 THHN for 3 hots, 3 neutrals, and 1 shared ground. I would terminate at the shed with a subpanel, three 20a breakers and a ground rod. From what I understand, seven #12 wires should work fine in 1/2 schedule 40 PVC without derating. Am I missing anything or good to proceed? Alternatively if I only wanted two 20amp circuits, could I run a multiwire branched circuit with 2 hots on opposite phases, a shared neutral, and shared ground to a disconnect at the shed without worrying about a ground rod?