David, generally you would use an arrow that is spined 10# lighter than the selfbow. This insures that the arrow will get around the bow during the paradox. You can leave the arrows extra long and/or use heavier than 125gr heads. Both will reduce the effective spine.
I draw 26" and shoot arrows that are cut to 29" to 30". For each inch over 28" you can reduce the effective spine by 5#per inch and for heads over 125 you can also reduce the spine weight but I don't remember that value.
If you are shooting hardwood shoot or cane arrows the natural taker of the shaft will reduce the effective spine weight by about 10#.