I read somewhere that the bowing of the pink or blue foam ( one made by owen corning, the other made by dow) after a cut is because of the production process of the foam. I have cut a few cores and most of mine were bowed. After skinning the cores they stayed straight. I've only had one that was no good, had a very bad twist in it after skinning with 1/16 balsa. On a tech note, has any one used titanium wire. Bass Pro shop is carrying titanium leader wire and stainless in various thickness.(.012-.020)