It's not clear whether you bought the plane as a user or as a collectible. The item was very inexpensive so you probably didn't ask for insurance, right? I do the same thing. It's a lot safer bet if you've checked the feedback beforehand and read what's been written about the seller's packaging. Otherwise, get the insurance. You can ask for them to ship the item UPS instead of USPS as the big brown includes the first $100 (I think) of insurance coverage in their shipping cost automatically.
Some bubble wrap and popcorn (you do mean styrofoam, right?) would probably appear adequate protection for what looks like a heavy and strong tool to someone who doesn't know tools. They probably wouldn't realize the brittleness of the cast iron.
What feedback you leave should be dependent on the seller's performance (was the packaging neglectful due to poor attitude or an honest mistake?), your performance (was it wise not to get the insurance and not to look into the seller's feedback beforehand?), whether you were really damaged, and what your relative feedback "strengths" are. The person with little feedback stands to be more affected by your single vote.
If I fellt like I had to point out the packaging to help future buyers, I'd give positive feedback, receive the seller's positive feedback, and then leave a follow up and mention the packaging.
R