I suspect you might be surprised by a time trial between a leather cross draw holster with strap in place and the Kit Bag. Would depend on the user of course.
Good point, I completely missed that part. The strap either makes it a two hand operation, or slows the draw while the gun hand releases the strap first before drawing. I tend to keep straps undone for that reason, only snapping them down if I foresee a reason. IIRC Elmer/Skeeter/Jordan used the same approach with their strap holsters. I'm definitely not them, but why reinvent the wheel if they've noodled out the issue already.
I remember one campout where I left my EPS Tanker strap undone, and I got a few helpful reminders and silent glances from friends who were from "gun guys." One dude I met on the trail even asked me why I had a pistol in the first place. All this is completely avoided with the Kit Bag.
