I also hve a 31' draw but I normally shoot 65# bows. You can vary spine by adding weight to the tip. The higher the tip weight the lower the spine. You can gain a signifient amount by going with a brass insert that can add about 100gr. to your set up. This is not the same affect as adding anothe 100gr. to your tip weight as it is not sticking out past the end of the shaft. Keep this in mind when you screw a BH on tht is 3X longer than the Field point you have been shooting all year. The arrow won't be the same. Simple physics and common sense. Now my advice to you is to get some carbon arrows of your choie and start experimenting. Use different pt. weights and inserts. Always test your choice BH's as well. There is no "MagicBullet" for formulas of bows to arrows. Spine charts will get you close but you still need to spend some time tuning and experimenting to get perfect arrow flight. Feel free to PM or email me and I will help you to the best of my ability. Each arrow and each persons unique characteristic IE: release, tab, glove, anchor, grip, style of shooting, aiming,...this all has an effect on what arrow will be good for you. People that think they can "advise " people on what arrow will work best with limited info are doing nothing but telling you what works for them...Good info if you shoothe exact same bow and have the exact same release with a tab and hold dead on at 45ydsand anchor with the cock feather on their nose. Just tooooo many variables. Ya jus need to experiment and tweak. Sorry about the rambling but I see so many guys slammed when they don't shoot the exact same thing that someone thinks they should shoot.