I have been using the Us Hunter clip on unit for a bunch of years. I only "loose it" when someone i hunt with see's it and Borrow's it. lol (i give it to them and buy another)
I sit on a chair that is only 6" off the ground, (just enough to keep the cactus off your backside)
I place the shotgun in my lap, the feet on the end of the barrel and point it down wind. The feet on it, keeps the end out of the mud, sand, snow, ect.
I keep the rifle off to the side on shooting sticks.
I find that when i need a shotgun, you can't reach for it, when they are on you, they are on you fast. If i need the rifle, i have time to reach of is and the then it stays in my lap with the shotgun barrel out of the dirt on the feet.
I have shot a few doubles, and a coyote bobcat double this way. I find that if you are not sitting with the shotgun pointing down wind, you will be soon enough if something comes in to shotgun range. Then you just raise it and fire.
As for the US Hunter shotgun feet.. These guys are the worst advertisers ever.. They should be selling piles of these things.. I have a spare that i keep just in case something happens to mine and they stop selling it. For $15 or less, it's something you won't regret buying if you carry two guns or more to a stand. (I also carry a small 22lr pistol for those that aren't dead yet when i get to them. I don't want to ruin a pelt shooting a coyote or cat with a shotgun or rifle round at point blank. A 22lr in through the ear is fast and doesn't add a hole to the pelt.)