Transformers Optimus Prime Transforming Halloween Costume - tips? plans? etc?

Are there any general plans out there for making a transforming costume?
With a few weeks to go before Halloween and a bunch of spray paint and cardboard and possibly paper mache, I figure I might be able to whip up something for the company costume party.
Does that voice-changing helmet that I see on store shelves everywhere fit an adult size head? Kinda concerned cuz I have a big ass head (hat size 7 3/4)...
I am thinking of basing my own costume design incorporating elements from the following videos found on the internet...
My goal is to emulate the Optimus costume found at the end of this video:
http://www.youtube.com/watch?v=03vCVejaEd8
Now I know I probably won't be anywhere near as nice looking as those guys... but hey, I figure it's better than face paint and a pair of $2 vampire fangs.
With a few weeks to go before Halloween and a bunch of spray paint and cardboard and possibly paper mache, I figure I might be able to whip up something for the company costume party.
Does that voice-changing helmet that I see on store shelves everywhere fit an adult size head? Kinda concerned cuz I have a big ass head (hat size 7 3/4)...
I am thinking of basing my own costume design incorporating elements from the following videos found on the internet...
My goal is to emulate the Optimus costume found at the end of this video:
http://www.youtube.com/watch?v=03vCVejaEd8
Now I know I probably won't be anywhere near as nice looking as those guys... but hey, I figure it's better than face paint and a pair of $2 vampire fangs.