Don't feel too bad. I did the same thing once where I didn't ask enough questions and got a marquee that looked like swiss cheese when backlit. Sometimes you eat the bear, and sometimes the bear eats you.
I wouldn't hesitate from giving him negative feedback. Be prepared for him to act offended, claim that you didn't attempt to contact him, didn't ask enough questions, that he gave full disclosure, etc. Seems like the seller always ends up with the last word, and it's always a frantic attempt to discredit you. Just once I'd like to hear a seller say, "Ya know, you're right. I totally ripped you off."
I bid on a lot of parts recently, including a marquee. I asked the seller if it was cracked or broken in any way. I got a flippant response back. I kept my cool and said I only ask because you did not state the marquee condition. Seller backed down and said sorry, its in nice 30 year old shape, but that he was on guard because a buyer recently wanted money back from something he recently sold. In the end I got all the parts and the marquee just needed to be cleaned.