I carry IWB
and I dont use a retention device. But I have the patented FRD, the Flab Retention Device. It holds the gun strongly and snugly in a coccoon of processed cheese and twinkies. I use it for all my guns.
my suggestion, get a great belt, a good IWB holster and have several portions of banana cream pie and pepsi and you too can use a FRD.