I thought I might share my creation. This is a fully transformable Optimus Prime that I had created using the lego digital designer program. I'm guessing that he would stand about 12''-13'' tall judging by the height of your average lego.
It took me quite some time to develope this and I'm very proud of it.
I say it's fully transformable, but I have yet to have the extra finances to build it in real life, so I'm not sure how gravity might affect it or if it's complete debugged. Although, as I designed it, I did keep gravity and space for movement in mind as I was planning all along to build it for myself.
If you wish to view the actually creation in 3D, it is possible to download and view a version of it on lego's website under the digital creations. Just search "optimus prime".
Also, I say "version" because their are a few bugs in it that I have since worked out.
I guess let me know what you think.