The mast tabernackle I use can be installed on the older boats. Go to www.dwyermast.com and click on the DM-4 mast. (we use the DM-4 mast for the 15) You can see a photo of the tabernackle and pin assembly we use. The part number for the tabernackle is DH 2173. The part number for the pin set is DH 2174P. The pin is 5/16 and is stainless. It should be mounted 1 3/4 inches from the base of the mast. This system makes stepping the M_15 mast a simple procedure. Fair winds, Bob Boat Builder Boat Builder