Rhubarb Crisp

I made rhubarb crisp tonight with some rhubarb I bought at the farmers market here. It was only a dollar for a bunch and was enough for this recipe. http://www.food.com/recipe/rhubarb-crisp-93946

I did put in only 1/2 cup white sugar, and increased the oats to 1 cup. David and I both really liked it. I would add in more rhubarb next time. I had a bit over 4 cups this time, but it could have done with 6 or 8 cups.

Update: It works best with something between 4-6 cups. Also the topping is great with just the 1/2 cup oats as called for in the recipe.  So in future, just have between 4-6 cups rhubarb and 1/2 c white sugar, with everything else as written.

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gf and sugar free variant:
filling:
1/2 cup honey
8 cups rhubarb
1 tsp cinnamon
1/2 cup gf flour (bob's red mill)

topping:
1/2 c sucanat
1 cup oats
1/2 cup gf flour (bob's red mill)
1/2 cup butter

This was not very good. I used bob's red mill gf all purpose flour and it did not perform well with the wetness of the dish. It rose to the top to make a strange spongy texture on top. It has done this with a corn casserole too, which was a custard. So if I make this again I will use a different flour, maybe oat flour.
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gf variant #2

3/4 c sucanat
6-8 c rhubarb
1 tsp cinnamon
1/2 c oat flour (finely ground)

topping:
1/2 c sucanat
1 cup old fashioned oats
1 cup oat flour
1/2 cup butter

This turned out great.