One Letter sheet per inbox item?

Im currently on chapter 5 in GTD. I've been using actiontastic to capture inbox items and lists on pieces of paper.

What I don't get is that one letter size piece of paper per idea seems like huge wastage! Is letter size critical here? Is there any reason not to quarter a piece of letter paper and capture each item like that?

I love the idea of GTD, but the paper waste seems.. well... wasteful!