If you actually need an inch and a half I'd add a pad and a leather lace-on. The pad could add an inch, then the lace-on another 1/2". There is always the wooden butt extension, but if you're not going to let someone like Mark Larson do it, I wouldn't recommend it. Too ugly, otherwise.

Realistically, it's a Nitro Special. Move it and find anther 20 ga. with more suitable dim's.