I thought it prudent to compare, from behind, the ears of Ruby on Sunday morning and those of the apparently fake Ruby on the Friday night, and both with Bookhout.
(1) The ears of the Garage Shooter are thick at the top and thinner further down, with a respectably sized lobe, and they protrude.
(2) The ears of the real Ruby are uniformly thicker and flatter against the head and have a pronounced lobe. Little protrusion.
(3) The ears of the Friday night Ruby are uniformly thin and end in a very modest ear lobe, almost a "webbed" ear connection. The clearest film I can find is that in the Gary Mack piece.
I want people to think about the significance of there having been a Ruby impostor at the DPD on Friday. It means that Ruby was being set up, and it must have been planned well in advance. My hunch is that as soon as they decided to make Oswald the patsy they decided that he had to die ASAP afterwards. Remember that Oswald wasn't mentally impaired or mentally controlled, and he would have been a fierce, combative witness for himself in court. They could not let that happen.
The killing method they preferred was to have law enforcement kill him, that he should die fighting the police. And that's what they hoped would happen at the Texas Theater. And it nearly did. But, they must have realized that it was no sure thing, that Oswald might need killing the old-fashioned way. So, the idea of having Ruby be the patsy for a vigilante killing of Oswald may have occurred to them early on.
But, the most important thing is that the very existence of a Ruby double changes everything. And that would be true under any circumstances, even if we didn't know all that we do about Bookhout being the real shooter.