Excellent C-UM.

What I mean is, you envisioned the Prime Cab transforming a certain way to accommodate all of the add ons to become Ultra Magnus. Legs becoming shoulders, etc. I was trying to turn my toy into that mode, to see what it'd look like before you put all the things on.

Like the original UM, all it was underneath was the Prime cab, with the head revealed, and the legs folded down, but feet left alone. Then all the stuff was added on.

Catch me now?  

 

I just tried this. Basically transform the front cab section without doing the legs, turn it upside down, postion the legs out to the side with the toes pointing skyward and flip the side panels on the legs down.