I don't want the flexibility kermit has but than you can form the mouth a little bit The mouth doesn't to be stiff ......
It is true that the rubberplaten will tear easenly now you mention it.
What is gasket rubber ........ I tried to find it on the internet but pictures didn't solve the problem what it is. It looked like the round sanding thing out of the sandingmachine. Where do you buy it and is it normaly used for something else?

You might be able to find it in hardware store and it would be used to make gaskets for appliances or perhaps plumbing. Your faucet has small little rubber gaskets in it to keep it from leaking and they are made of rubber gasket. You might be able to find it at an automotive store that caters to restoring old cars. Another rubber that would be similar is used by shoe makers to apply a sole to the bottom of shoes. It is much like the rubber platen but is denser and normally a little thicker.

Jon I have a question for you (or others who can answer it)
You made Joshua (what a nice puppet, i love him) from the round head pattern, you changed a little bit. I looked two both the patterns and compared them with each other. The chin is longer and the tuck in the mouth maybe changed a little bit too. So I was wondering if your mouthplate made the head more in a point (how do we call it). If that is so the mouthplate is more important than I thought...

All the modifications are all due to the shape of the mouth.

I decided the shape of the mouth I wanted and when I installed it in the head the result was that the head is not round.  I think that I did have to adjust the bottom jaw of the head a little to match the mouth.

The round head pattern is very versitile.  Change the shape of the mouth and the look of the head changes.

mmm that's very nice......that need experimenting on my side.