Preheat oven to 375 degrees. Prepare pastry for a single-crust pie and line 9" pie pan. In a small mixer bowl place sugar, flour, butter, eggs and vanilla. Beat until smooth. Pour a little on bottom of pie shell (About 2/3 cups).
Place chopped rhubarb on pie crust and cover with remanning custard filling. Place on a 375 degree oven and bake for 25 minutes. Remove from oven and top with crumb topping. Return to oven for an additional 10 to 13 minutes, until golden brown. For crumbs place sugar, flour and butter into a large mixer bowl. Mix until crumbs from. Add pecans, coconut and cinnamon. Decorate top as desired.