Are the carry-on standards the same between airports? The reason I ask is because I know at O'Hare (I'm in the Chicago area) they have these little kiosk-things that measure your luggage and if it's outside the lines, into the hold it goes. I don't know if those standards are universally enforced, and I've never had a situation where I was stridently opposed to checking a piece of oddly-shaped luggage.
When you did your travelling, was the iBook your sound source for the Zendrum? I've got an entire pedalboard for my rig... I don't consider any part of the system redundant and it's a soft shell bag, not a flight case. I have similar concerns for that but I doubt they'd let me get both of the items through.
Great idea about bringing the manual. Hee hee... kind of reminds me of when you have to prodce papers for an animal or something!