"I think you'll find the 1 piece Beeman mount far less likely to move than a 2-piece mount. Even with a stop pin or bar, it can happen. The full length base of the 5038 provides a lot more area for gripping the rail, so it will absolutely not move."
The same can be said of the BKLs. I have the BKL 263s installed on at LEAST ten spring air rifles; one TX-200, one Pro Sport, one Goldstar, two R-1s, one HW-77, three Supersports, and one Supersport Lightning. I have used them on my Venom Tomahawk .22, one of the hardest recoiling rifles ever. Guess what, the Tomahawkl has NO stop pin holes or cross-bars of ANY type. I certainly wouldn't go out on a limb and carelessly recommend ANYTHING. I know they'll work. They have worked without exception.
So let's assume Guy "X" buys the Beeman 5038 for some fifty odd dollars. What if he doesn't LIKE the Patriot/Kodiak and sells it. What does he do with the fifty buck mount? If he bought the $35.00 BKL he has a mount that will work on practically ANYTHING.
Also let's consider the fact that the BKL can be mounted ANYWHERE along the dovetail, not just lined up with a grove.
" I think you'll find the 1 piece Beeman mount far less likely to move than a 2-piece mount. Even with a stop pin or bar, it can happen."
The answer is YES, with any 2 piece mount except the BKL 263.