Christine, I love this idea. Most of my artwork is A5 in size. I totally agree that the smaller size pushes you more and also allows you to really experiment. I'd be up for trades here. Size-wise my preference would be greeting card size (5x7 inches).
For the past few weeks I've been thinking about it,
I did not use exact or cut paper, however, almost all the drawings I made on a sketchbook in the middle between a5 and a6 in size.
helped to use tools that I used little or new things, the pen with the white pen. use the pencil before the ink.
i reused bic in some designs. so it helped draw when i had no idea what to draw, or not feel like.
the pleasure of experimenting, using things I used less. and also the convenience of using the mobile phone to look at references, this is more convenient for me (I prefer to draw with the reference on the left of the sheet even if it is small, for references I often use online photos, looking at PC monitors or mobile phones.) but it leads me to draw a lot smaller.
I thought I'd post here so, thanks PaintBoss, a warm greeting.