Nerd Lizard Design

OK. So, the big guy is all fused. He's out in the garage having a magical time getting flattened. I need to customize his backer. As you can see from the picture, he's too tall for the current backer. I'm trying to decide whether to with something flat or raised. I'm worried if I do raised he'll warp more and it'll look real bad. Where the flat would be OK. Hmmmmmm.