If you divide the deck into 3 groups, you can store a number 2^17 in each register (~131,000) and have an out register for recording the results of adding/subtracting the other two registers. And have a few cards left over to fill in blanks as you go. So now you're not just encoding messages, but you're able to do something useful with them and write programs.
You can double the size of each register by representing 1 or 0 as card or NO card in each place, and get up to numbers 2^34 or 17179869184. If you switch to base 3, you can have a card face up or face down, or not there and achieve 3^34, or 1.7x 10^16.
Or if you go to base 5, with card face up, upright, face up upside-down, face down upright, face down upside down (if the cards support this platform), or absent, then you can achieve 5^34 or 5.8x10^23.
Base 7: turn cards sideways. Base 25: turn cards to various discernible degrees, including face up, face down in all clock-face configurations, plus absent.
The point is, you can do a whole lot more than just encode 52 bits. You have a much wider range of possibilities if you get creative with your representational systems.