Roll out half the pie crust pastry to a circle about 11 inches in diameter, and fit the crust into a 9-inch pie dish.
Place the pie dish onto a rimmed baking sheet.
Whisk together 1/2 cup of sugar, 1/2 cup of flour, and 1 teaspoon of cinnamon in a bowl. With a pastry cutter, chop in the butter until the topping resembles crumbs; set the topping aside.
In another bowl, stir together the strawberries, rhubarb, 1 1/3 cup of sugar, crystallized ginger, 1/4 cup of flour, nutmeg, 1/4 teaspoon of cinnamon, and salt until thoroughly combined; beat in the eggs.
Roll the rest of the pastry out into an 11-inch circle, and cut the crust into 1/2-inch wide strips. Spoon the strawberry-rhubarb filling into the bottom crust, and sprinkle the crumb topping evenly all over the filling. Moisten the rim of the filled bottom crust with a bit of water, and lay the two longest strips in a cross in the middle of the pie. Working from the next longest down to the shortest strips, alternate horizontal and vertical strips, weaving the strips as you go. Press the lattice strips down onto the bottom crust edge to seal, and trim the top crust strips neatly. Press the crust edges with a fork dipped in a little flour to make a crimped edge.
Bake in the preheated oven for 10 minutes, then reduce heat to 350 degrees C (175 degrees C) until the pie is bubbling, and the crust and crumb topping are lightly browned, 45 to 50 more minutes. Cool pie at least 1 hour before serving.
