MiniYaYo

So I have 3D models downloaded from Robin and I am trying to create a hair base. Whenever I merge down a layer onto the 3D model my hair base layer shrinks and half of it does not show. I use photoshop cs5 extended. This is what it looks like when it isnt merged.. http://prntscr.com/ovofz5 & this is what happens when I merge it.. http://prntscr.com/ovognm .. I really hope someone can help me fix this problem!!