flour sub in amanda's plum tart?

1/2 cup oat flour...sorry for omission. And I simply ground whole rolled oats for the oat flour...worked like a charm.

Reporting back...for the 1.5 cups AP flour, I subbed 1/2 oat flour, 1/4 cup potato flour, 1/4 cup hazelnut flour, 1/8 cup tapioca flour and 1/8 + 1/4 cup brown rice flour. To accommodate for the fat in the hazelnut flour, I lessened the vegetable oil amount to 1/8 cup (versus the 1/4 c Amanda calls for in the original recipe).
It was great- sturdy, crumbly, good. Mom thought it was terrific. If you didn't know this was GF, you wouldn't guess!

awesome, y'all, thanks! will let you know what formula i end up making/using!!

Also, please see Juanita's comment on this Peach Tart recipe -- which has the same crust: http://food52.com/recipes/14217-peach-tart

Here's a great starting point for dinking around with gluten-free AP flour: http://glutenfreegirl.com/2012/07/how-to-make-a-gluten-free-all-purpose-flour-mix/
The King Arthur gluten free multi-purpose flour is supposed to be good. It uses a blend of rice flour, tapioca starch, potato starch, and brown rice flour. I'd probably start with those ingredients, though would likely work oat flour into the mix.