"You'd have the same issues with a 40-space/40-circuit panel."
Larry, Who makes an AFCI twin CB?
The point Markp is making is there won't be an application for a 20/40 panel if the only single pole breakers available are full size. A 20/40 will just be a 20.

[This message has been edited by Fred (edited 09-21-2006).]