Hey Mark,
You can pull a trailer like yours with your 853, but you can't use a ball. If you look at a BCs trailer, the pivot point only allows horizontal left and right movement. It does not allow for vertical movement like a ball would. If you just stuck a ball on the 853 somehow, you'd have to constantly hold up or down on your handlebars to keep the tractor level.
I know of one guy who took a trailer like yours and made an adapter to use it on a BCS. He basically took a two foot piece of square tubing, bolted it under the drawbar of the trailer with a pair of U-bolts, and made the pivot off of the end of the tube. It's very nicely done. He has pics on the Yahoo Groups - BCS users. I'd put the photos up here, but I don't really think it's right to take someone elses photos and spread them around.