Creeker
In the proposed stage, there are 5 strings, including 2 revolver strings--whether you are shooting GF or not---because all shooters are changing firearm types 4 times. Yes, the stage conventions, as noted, require that the revolver be returned to leather at the end of the string, BUT those shooting GF style are expressly forbidden to reholster with the intent to use the revolvers again and so must shoot double duelist unless stage design accommodate grounding the pistols. Furthermore, as the relevant stage convention pertaining to a single revolver being deployed specifically notes, it may be overridden with instructions requiring or permitting the revolver to be staged rather than reholstered. It is not necessary that the revolvers first be staged in order to permit/require them to be staged after use. For the sake of clarity and consistency, in writing your stage instructions, you could simply require all shooters to stage the revolver(s) at the end of the first revolver string. Or you could permit it for those shooting other than GF style, allowing them the choice either of reholstering the first revolver or of staging it until the stage concludes.