Oat Fiber Question

I make a sourdough whole grain sandwich bread with which I am very happy.  The recipe is given below.  I would like to increase the fiber content still further by adding 4 oz of oat fiber.  I am looking for advice on what changes I need to make in water content, as well as what changes to expect in the consistency of the bread.  And, finally, if adding oat fiber to my recipe isn't predicted to make a good bread, has anyone tried to cook stews or soups with oat fiber?  Does it act as a thickener, or make slimy globs, or burn to the bottom, or what?

Pre-ferment:

4 oz milled whole rye
4 oz milled whole winter wheat
5 oz water
1 cup starter

Pre-soak:

16 oz milled whole spring wheat
4 oz non-fat Greek yogurt
8 oz water
[add oat fiber here?]

Dough:

Pre-ferment minus 1 cup
Pre-soak
1 tsp salt
1 tbsp olive oil

Bake covered for 20 minutes at 450F, followed by 40 minutes uncovered at 350F.