Glock 20 or 21 Into 9mm?

[ar15barrels]

Has anyone converted a Glock 20 or 21 into 9mm? I know that it's fairly simple to convert the a Glock 20 into either 357 Sig or 40 S&W and since you can convert a Glock 22 or 23, which has the same bore diameter as the Glock 20, into 9mm I'm wondering how easy it would be to convert a Glock 20 or even a Glock 21 to 9mm?

First issue is slides.
The slide rails for the large frame (20/21) are not the same as slide rails for the standard frames (17/22) family so you can't stick a 17 slide on a 20/21 frame.
Next is magazines.
Large frame magazines are not made for 9mm.
So while you might get some 9mm rounds to stay in a 10mm magazine, they are nowhere near optimum.