I read over the forum post & to be honest, I really do not see the FN Five-Seven 5.7mm lending itself to IWB type concealed carry.
The pistol frame & large sights would seem to be difficult to tote around for most sizes/shapes/frames.
To my understanding FN does not offer a compact or sub-compact concealed 5.7mm semi auto pistol yet.
As for IWB type rigs, see
www.COMholsters.com www.Blade-tech.com www.Safariland.com www.Highnoonholsters.com www.Galcogunleather.com www.Donhume.com .
ClydeFrog