Re: IWB and retention straps
Anybody attempting to take your concealed carry weapon from you should have three hurdles to clear.
1. They need to know that you're carrying.
2. They need to know where you're carrying.
3. They have to clear your cover garment(s).
Most angles of approach are unnatural, and biomechanically clumsy. Carrying concealed is a heavy retention system, in and of itself. Adding a retention strap will impact you on every draw, but will have no opportunity to hinder an offender, unless you make it known that you carry, make the position of your weapon known, and fail to respond to substantial enough garment clearing for an offender to gain access to your weapon, and to visually confirm the position, THEN attempt a (likely clumsy angle) draw.
I advise against retention straps for IWB.