RSVP Postcards

I am considering making RSVP postcards - to insert in my pocket-fold invitation.
Size will be 3.5 v 5.

Has anyone done this before?
Would I word a postcard the same way I would word a RSVP with an envelope?

Any and all advice/ideas is appreciated!!!
Thanks ladies!

My cousin made my invites and we went with a postcard RSVP card. On the lefthand side we put:

Please respond before the ________ of _______

M.________________________

Will attend _______

Thank you!!
how big where your postcards?

My postcard RSVP looked like this:



I designed them and then ordered them from Vista Print. I was really happy with the way they came out and they weren't expensive at all. The size is 5.47' x 4.21'. If you check retailmenot.com, you'll usually find a coupon code for Vistaprint. HTH.