Apparently the two card sizes are referred to as Bridge (the narrow kind) or Poker (the wider ones).
This page has a nice writeup about the two sizes. I'm learning a lot, writing these games!

I'll probably do a bit more tweaking to get the Poker size a bit more exact. At the minute my two ratios are 1.33 and 1.55, whilst they're "supposed" to be 1.4 for Poker, and 1.55 for Bridge.
All of my earlier coding was done with the Bridge numbers, so that's pretty much spot on, but I'm now wondering what that tiny 0.07 difference for the Poker might look like.

So, yeah, I think I'm probably about to do that all of today's work, all over again, with another slightly different set of numbers!
Oh the fun!!