Lex,
Go to Lowes or Home Depot and pick up some 1 inch PVC. The issue is that the black collars on the posts will slip down when the PA is under load. Here's a picture of one of my Hobie HD Carts. Cut a spacer about 3/4 of an inch and put it under the black collar. My PVC was cut by hand and isn't exactly straight, but you get the idea. Making the PVC spacers will ensure your tires never rub the hull. Your space size might vary. You want just enough room above the deck so you can slip the retaining pin in.