Laura,
I haven't used flax o meal but looked up the ingredients.
From what I saw it looks pretty good. From what I know those "hidden carbs" are mostly found in sugar alcohols. I didn't see any in the flax o meal cereal so I think you're safe.
I know LC Sponge uses flax seed. If she doesn't get around to this post you may just want to post it on her journal.
Maybe she also knows about flax o meal.

Take care,
Heather