I have previously installed a 25' x 25' square made of 6x6s. There are 2 courses and they overlap with 6" offset. They are screwed together top down and at corners. It was originally made (by overcautious dad) for my 3 yr olds swingset/fort/slide and filled with 6" of wood chips. Do you think this would require any extra bracing if I was going to put down a liner and make a rink? Will a liner or reasonable strength perform OK over chips instead of grass?