Pistol to Rifle Reconfiguration, and Back Again

18§921(a)(8) defines the term “short-barreled rifle”

The term “short-barreled rifle” means a rifle having one or more barrels less than sixteen inches in length and any weapon made from a rifle (whether by alteration, modification, or otherwise) if such weapon, as modified, has an overall length of less than twenty-six inches.

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If you use a conversion kit to configure what was originally a pistol, into a rifle, can you then configure it back to a pistol without it becoming a short-barreled rifle? It's my understanding the the ATF is currently saying that you can't. Does anyone know the history of the different positions the ATF has taken in regard to this matter. Have there been court cases that address the reconfiguration of a pistol into a rifle and then back to a pistol?

I have read United States v. Thompson/Center Arms Co, but unless I missed something, it only says that the unassembled components don't constitute a short-barreled rifle.