One problem with "Big-ass Enter" keys is that unlike other keys, the arrangement of the stabiliser(s) is not entirely standardized.
Max Keyboards, Gateron and Tai-Hao have keycaps that look as if they are compatible with Steelseries' keyboards. Those have stabilisers like ANSI Enter keys and a long peg in the middle of where a 1.5u Backslash key would be.
The lower part of the keycap should be compatible with an ANSI keyboard... but I think that the peg is too wide to fit inside the drill hole in the PCB for the Backslash key's switch. The best solution would probably be to mod it: cut it short, sand it to the exact size and then cut a cross in it to accept a Cherry MX switch.
BTW. Cherry itself has made "Big-ass" backwards-L Enter keys but those have had the stabiliser bar on the vertical - in the middle of the 1.5×2 rectangle. They are not compatible with either ANSI or ISO.