It's plenty thin, but the shape of the trigger guard for the 709 precludes it from fitting in most of the PF9 holsters I tried it in.
I can verify that the Taurus 709 fits perfectly in Glock 26/27 Galco Summer Comfort leather IWB
and also fits in the Uncle Mike's microfiber IWB open top that's made for Glock subcompacts (#12 I believe)
I find the microfiber really comfortable and it doesn't bulk up the IWB feel like the Galco SC can, but the plastic clip on the Uncle Mike's does allow the entire holster to shift more than I'd prefer.