We are a commune of inquiring, skeptical, politically centrist, capitalist, anglophile, traditionalist New England Yankee humans, humanoids, and animals with many interests beyond and above politics. Each of us has had a high-school education (or GED), but all had ADD so didn't pay attention very well, especially the dogs. Each one of us does "try my best to be just like I am," and none of us enjoys working for others, including for Maggie, from whom we receive neither a nickel nor a dime. Freedom from nags, cranks, government, do-gooders, control-freaks and idiots is all that we ask for.
We impatiently made some a month ago and a little too green and tart, even w gobs of sugar. Last week's was sublime! We used a similar recipe. Crystallized ginger is good to keep around in case your fresh ginger root has got lost in fridge and gone bad since you made Thai food. I put pats of butter in the rhubarb part, and a handful of flour and swirl it around w the sugar and spices and rhubarb before putting the crumble topping on. This is because I loathe cornstarch, but my garden's variety of rhubarb exudes so much juice you need to thicken it a little. I use cinnamon and nutmeg in the crumble mix, then add three or four handfuls of pecan halves to the topping w a dash of salt. Even confirmed rhubarb haters will usually try it when they see pecans.. It's yummy.
My recipe for the topping has rolled oats in the crumble mix. Equal parts of flour, brown sugar, and rolled oats mixed into enough butter (do NOT EVEN THINK of margarine) to allow mixture to clump. Otherwise much as you have said. Do often, when I have them, add strawberries to the base as well.
My grandmother's recipe for fruit cobbler topping uses only 2 TB of butter/oil, with an egg stirred in, a 1C each of flour and sugar.[I reduce the sugar somewhat, substituting in an equal amount of flour.] Sprinkle the topping on the rhubarb/fruit and then sprinkle a quarter cup of water on the topping. Works for any fruit- rhubarb included. I add some apples to the rhubarb.