I am creating a 11x8.5 horizontal WHCC book for a guest sign-in book with 10 spreads plus the opening and closing page. I am being careful to leave at least 50% of each spread open for signatures and comments, but the wedding has 200 guests. Is this going to have enough space? It is yearbook style with no lines so I am guessing that the guests will write short notes on the book.

plenty of room.

i did a 10x10 for a 350-person wedding ...
http://www.wedoodledo.com/gallery/guestbook1/

people don't write as much as you'd think.

they seem to just like to look at the pictures!

Thanks Robin. I am thinking it should be enough space.

For my own wedding we had a sig book and we only had about 100 guests but I swear I think we only got.. 30 signatures, if that many, lol. So not that many. I designed a book for a couple who's wedding is in july. Originally they said about 150 people but it's looking more like 220 but I still think I left them plenty of room for the signatures they'll get. I did the WHCC book like you, but I put 22 pages total I believe.

Good to hear Brandi. We are at 22 pages total as well. I think it should be plenty.