.....and as I pointed out, there is no size description for a cyberdeck, only a shape. The description Xenon used as "two deck of cards " is not used anywhere, that I know of, at least not this edition. Certainly in any picture I've seen(mostly from editions 1-3), they've been much bigger, at least the size of desktop keyboard, but often bigger.
In SR 1-3, before the wireless matrix and AR, they were indeed much bigger.
In SR5, see page 229, right column, first paragraph under "Cyberdecks":
"...just about any shape that has the same volume as a small book."
So yes, the RCC is distinctly bigger.
Personally, I'd allow someone to install an RCC in an implanted large smuggling compartment.(Cost: 8000, Required Capacity: 5, Size: Breadbox) It wouldn't be removable, but would be permanently installed in the space. But that's my houserule.