Nope, no difference in the actual carbon. Same crank, except Record gets the foam sucked out as you mentioned. A couple different dealers have told me this.
Because the record crank arm is lighter and the foam lends no strength, then yes, there IS a higher strength to weight ratio for Record, but not because you're adding strength--you're just subtracting weight that serves no structural purpose.
The other differences as you pointed out are the slipperier chainrings and different bolts.
__________________
"Unless he was racing there was no way he could match my speed."