IT IS OFFICIAL....
A secret jib park has been set up at Blue Hills. In it is a down rail, c rail, flat down box, and a flat box. I'm not sure about the dimensions, but none of them are shorter than 10 feet. All of these are courtesy of the guy I met.
The location is in between the trail "Tropie", and the top of the bunny slope. It used to be used as a cut through for ski patrol, but hasn't been used in years.
Here is a picture, but it might not work, so click the link: