Substitution "Rules" for Running Clock Games

It is just about Fall Ball time. A number of the unofficial games have unofficial rules like 30 minutes running halves.
I have played it both ways (liked both ways), and am just curious to get some feedback...
Should teams be allowed to request a whistle for dead-ball substitutions during a running clock game?
I have played it both ways (liked both ways), and am just curious to get some feedback...
Should teams be allowed to request a whistle for dead-ball substitutions during a running clock game?