Got the kncok-off sunglasses yesterday, and have learned the error of my ways...
The glasses fit my head almost like kid sunglasses (not that bad). But then again, I have a big head (7 3/4 hat size), and I'm certain Cruise has a fairly small head (he's what - all of 5'8"...?). And the glasses are most likely undersized anyway.
All that being said, I have to squeeze them pretty tightly into the main tube. I thought the tube would be big enough based on the fact that my regular glasses fit fine. But I have to compress the sunglass notably to get them in, and the tailfin portion will not go in when the glasses are in there.
So...
Net result is that the center/main tube is a bit too small. Part of the reason why I was seeing it as not fat enough, I'm sure.
However, using the materials I had available (this was to be a quick and easy, not dead-accurate project), the next size up would be too big. As a reminder, the main tube is a pre-cut length of ABS pipe from Home Depot, found in a stand-alone cart/display.
In the end, I'm mostly OK with the prop as is, and may still devise a way to get the tailfin piece to fit with the sunglasses in.