I email Mean Arms and got the following response about the EndoMag.
Although we have not tested that particular upper with our EndoMag, after a quick search, there does not appear to be anything alarming with that upper we would be worried about. Our EndoMag Conversion Inserts should work with most standard 9mm blowback uppers. You would need to purchase the Ejector Version EndoMag Conversion Insert. If you want to give it a try in your upper, we proudly stand behind all our products with our Bulletproof Lifetime Warranty and we offer a 30-day full money back return policy, when ordered through our website, in the event of an issue.