I have tried Purina FortiFloria with minimal success along with a wide variety of others, both as food additive and treatment for problems. I didn't find one single powder that worked for issues we've had here.
The one I've had the most success with and constant success with for extremely loose stools in Geneva(rb), this product stopped them, and minor issues for the others when I brought them home or with antibiotic treatments, and even for Scooter's swollen lip allergic reation is Vetri-Science Fast Balance-GI. It consistently worked.
The pitas will voluntarily consume what I give them of this, while hairball formulas are summarily rejected. So there is something about this they found acceptable.
Ling is a scarf & barf and I'll give her a tiny amount to settle her tummy down when she'd done that.
Maybe it has no meaning as far as using it, and maybe it's the foods they eat plus this, but I don't have hairball barfs here and I've tossed the hairball formulas. I've never seen Scooter or MK barf a hairball after I started using this. Ling's aren't hairballs ( I examine her barfs) but from "inhaling" foods.
It's a bit pricey, but it ended up cheaper using something that worked than all I spent on trying to find products that worked alone or ones they'd actually allow mixed in their foods:
http://www.onlynaturalpet.com/products/Vetri-Science-Fast-Balance-GI/125021.aspx