RSVP

I am starting to get my invitations in order and I have a question about stuffing them. Do I put the RSVP card inside the return addressed envelope or put the RSVP card in the flap so they can see it.
Second question, were my invitations supposed to come with tissue? I just realized there is no tissue paper!! Does it matter?

Just in the flap so they can see it and no it doesnt matter. I havent gotten an invite with tissue paper in a really long time so dont worry =))

I put them in flap. .and mine came with vellum and we didn't even use it. . just looked unecessary