I had not heard of the Rattler before - I just looked it up and it says it has a fixed magazine, just like the K1 and SK-19 do . . . . but they do offer a version called the Sidewinder and that one says the mags are removable. Of course the configurations are quite different to pull that off, even though at first glance they do look similar to each other.
Until they do this not really much of a thing.Travis has the right idea! As far as the Carbon stock goes, I was just on New England Airguns site & they show 7 different stocks for the Huben. Camo, Colored & 3 in carbon fiber. All show in stock & are $250.00 each. https://www.gatewaytoairguns.org/GTA/index.php?topic=176255.msg155993273#msg155993273