The thickness the Stingray will cut is quite limited.
Ages ago, when I got married, I did the invitations by hand (money was tight, and I figured I was an award-winning graphic designer and aspiring calligrapher) and part of that was an inner envelope. Took one out and measured it and made a file:
envelope.c2d (11.1 KB)
or for the tool definition below:
envelope_8283.c2d (52 KB)
which, if I’d only had a machine back then would have saved my cutting out some 200 of them by hand:
(the actual material used for the invitations was a translucent EDIT: artificial vellum which made for a really nice effect)
For a tool definition, something like to:
should be a good starting point.