Well Buster, I'm glad you opened this up. I wasn't going to right of the bat. You are correct there is only the one bolt connecting the receiver to the ATV. I did not like this idea at all, but was out of options. And like you said, the BRP receiver is smaller. I need 2" to be functional. (save the comments fellas.)
You hit the nail right on the head though with what I was thinking. I want to weld the the hitch to the atv to prevent that slipage you were talking about. Not only is that danerous, but just a pain the arse. With the frame design of the Outty and Gade, I'm not sure there any other options. Oh yeah. When I weld that baby to the ATV, it will eliminate the holding bolt which will allow a standard 2" truck receiver hitch to fit in there. Other wise I would have had to cut one down to size nor will I have to buy spares.
Another note worth mentioning is that the holes on the hitch are notably small. I measured my ball bolt from my truck hitch and it was a 1" Diameter bolt. The hole on the Moose Hitch is around 3/4". I'm not sure if you can buy a 2" ball with a 3/4" bolt???
The bottom line is, IMHO, without some seriousl modifications, this hitch will be dangerous and combersome. However, I have not tested it. I will do that before I make any changes. Another defensive statement would be, this is an ATV, not a work truck. After using an impact wrench to secure the receiver it should take some serious pressure (like that not recommended by the manufacturer) to move it. It has a star washer between the two to create a bite and eliminate or minimize movement.