A good floor tiller will go a long way!get it really close by eye and feel.put the shortest string that you can fit without struggling to much.exersise it on a tillering stick maybe pulling 10" for 20 to 30 times ,hook it on a notch at about 10" ,take a few steps back and assess quickly(maybe take a pic).this all has to be done as quick as possible.mark it with a pencil where to remove wood and where not to.when your happy go to a low brace of 3",exercising well as you go making sure to sight down the limb with every chance you get to see where the wood is beginning to show signs of stress(set).you would see early on in your case that the outer limbs were working to much and starting to deform.study the brace very closely as this will speak volumes as to how even your tiller is.I constantly run my hand up and down the back juring the whole process to feel for splinters.return it to the tillering stick until you are confident to go to brace height.if you don't understand some of the terms I have. Used just ask ,somebody will fill you in(not sure if there is a bow building glossary on here somewhere?) There are many ways to skin a cat and this is just one.