Aviator holster
Quite a few years ago, I purchased a repro "aviator holster". It is a chest rig, and a bit more minimalist than a "tanker", as there is no second strap that circles the torso. I use the aviator for my Ruger B-hawk, and occassionally one of my 4" N-frames.
I liked the rig from the start. It's biggest plus is that you can simply duck in and out of it. A snap on the back of the holster can secure it to your belt, or you can just let the thing hang from the main strap. An underarm rig has always felt just like that to me, I've got a gun literally in my armpit...the aviator and other chest rigs bring the pistol forward enough that I loose that sensation, and it seems to carry better, more central too.
On the ATV, mtm bike, and in and out of the 4wd, the aviator keeps the gun out of the way seats, handlebars, knobs etc, and is not rammed into my hip like a conventional waistband holster.
It is not a concealment rig, and with its external retention strap, is not fast either, but seems very practical in the field and out and about.