I've never sent out my cards on *real* postcard sheets - always been cut down from larger sheets or regular size sheets if I've had them in stock. I admit I do stick my labels (fullsize) which does add to the thickness a little, but have also just used 2 smaller ones on many as well.
Originally Posted by Ricus.stormfire
And many of the cards I've received haven't been postcard stock either and still fair very well in the post.
It's rare that I receive damaged postcards in any form, unless it has been soaked in the rain at some stage prior to delivery.