Yeah, Olivia's test run idea is smart, but I'd take it a step further. You could actually ask a bakery to do a test with you. See if they'll make a small sample tier with their summer buttercream and let you pick it up on a hot day. Watch how it handles the car ride home. Any good baker should be confident in their warm-weather recipes. If they hesitate, that's your answer right there. It's a bit of extra work, but way less stress than a total collapse at the event.

Honestly, three hours for a zip tie seems a bit much, even compared to @stella_rodriguez's story.

I get where you're coming from about tech overcomplicating things, but I've had the opposite happen. A new system at my own local spot cut the wait time for a fresh pot in half. Sometimes the change is just about getting used to it.