Where the doors are to the outside of skater island are some verts get ontop of the first vert with the double shaded wall. Now wallride the wall doing low wallrides so that you wallride into the floor do this on the lighter patch of wall and you should be able to get behind the wall. This can take a few goes so dont give up. When inside move slowly as areas of it are bouncy. Now get someone to go outside, the cannons should blow the ramp away and you will be stuck in the wall.
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