Optimus Prime costume help please!

[smallville fan]

Hi, I've got a costume party coming up, and I really want to go as Optimus Prime(G1 version preferably, but I like the 2007 movie version as well)

I've looked everywhere on youtube and other video sites for how-to's on making a costume, I'm trying to make a costume(that actually transforms) where both the robot-mode and vehicle-mode look good.

The costumes out there either have one where the robot-mode looks really nice but it doesn't have a vehicle-mode or one where the vehicle-mode looks great but the robot-mode looks like crap.

Help me out here people, can someone tell me how to make a really good costume

I really want to get something like this going:

http://www.youtube.com/watch?v=akNJ6S2UqsE

please please help me out!