I glued all my spacers and rim together, then turned the whole thing upside down and then drove two tacks (one in center front and rear) through the spacers and 1/2 way through the rim (the tacks were just long enough). Next I glued and clamped the unit to the deck. No sliding and everything was uniform. I cheated by cutting and using one-piece spacers instead of trying to glue many halves together.