Largest pistol and easily hidden seem like an oxymoron, so I do it IWB with a Hidden Hybrid Holster and an XDm 9mm 4.5 with Viridian X5L, and oversized pullover shirt. The holster is between 8:30 and 9:00 (I'm a lefty), which puts the butt of the grip below my armpit and the muzzle/Viridian Kydex poking slightly outward close to the bottom of my left jeans pocket.
The grip butt is not an issue, but I have to be careful that my shirt doesn't ride too much higher than the bottom of my pocket, a strange place for a bulge.
Suppose I could always say I had a torque-wrench in my back pocket if anyone asked, and I'm looking for sockets to fit it...
Driving is not an issue as I pull up my pants slightly when entering my car.