Titans Return question

I just bought my first Titans Return figure, deluxe Hardhead, and while his head is a decent proportion to his body, I know that heads can be interchangeable between different size classes.
The Leader class toys seem to get around this by having an extra shell that goes around the Headmast- I mean "Titan Controller". Kind of like G1 Scorponok or Energon Optimus.
But what about the Voyagers? Do they have the shells too? Are their Titan Controllers slightly bigger? Do they just have proportionately smaller heads? Is there some other explanation?
The Leader class toys seem to get around this by having an extra shell that goes around the Headmast- I mean "Titan Controller". Kind of like G1 Scorponok or Energon Optimus.
But what about the Voyagers? Do they have the shells too? Are their Titan Controllers slightly bigger? Do they just have proportionately smaller heads? Is there some other explanation?