Bry,
I will see what the experts say no doubt they wont reply.
With quotes like that, I for one wouldn't answer, even though I do have some experience of silicone moulding that were a lot more complex that you are trying to do.
If people want to reply they will, but trying to force them into it will guarantee you don't get replies.
You also don't give a reason for asking why you want to make them. If it is for that pressure vessel in your other post, then anyone even offering to help would be leaving themselves wide open if anything went wrong with such a dodgy exercise.
There are times when you do it yourself, and other times when you need to dig deep into your pockets and let the experts do it for you. Things like that are expensive because of all the R&D and hundreds of man years experience that goes into producing them, and you are looking to make it in a kitchen or back yard workshop.
Bogs