Make a double recipe of Pie Crust
1 ¼ sugar [I use less sugar - about ¼ c sugar for each cup of rhubarb]
5 T flour
½ to 1 t cinnamon
1/8 t salt [I omit]
Spread half (or a bit less) of this mixture over a pastry-lined 9 " pie plate.
On top of this mixture add
4 cups or more sliced rhubarb and strawberries [I use ratio of 3:1 rhubarb to strawberries.]
And sprinkle the rest of sugar mixture over top. Sprinkle with:
1 T lemon juice
Roll, fit and be sure to seal upper crust. Dot with 2 T butter (optional) [Mom and I omit butter. Cut pattern in top of crust from which steam can escape.] Bake on lower shelf in hot oven, 425 degrees F, 30  – 40 minutes.
Instead of making a full top crust, Mom usually makes a lattice crust, cutting strips of crust and putting them across the top in a criss-cross latttice pattern. I think is my top crust choice.
Verdict? The liquid was certainly thicker, almost gelatinous, but I found the crisp too heavy for my taste. My preference is for the more delicate original recipe, and think this will be true for the pie too. Maybe just attributable to familiar comfort food.
2016 Update: See also and Best Ever Strawberry Rhubarb Pie/Strawberry Rhubaarb (Ginger) Crisp and Make Strawberry Stains Vanish