Merc1
Premium
Nope. The chassis reinforcements are in the door panel (and in the trunk) to give extra torsional rigidity so it has nothing to do with the chassis unibody construction. It has a B-pillar as well, which coupes typically don't have (for added rigidity). My friend's similar sized E53 AMG does not have it (and it weighs 4600 lbs).
Ok great, I don't get the point of the discussion anymore really. The RC is too heavy to form the basis for the Supra, and I found it to be dull to drive. None of that is going to change so any number of reasons or excuses as to why it is this or that is really matterless at this point. It's hodgepodge of other Lexus cars underneath and it shows in the driving in MY experience.
M