I think the wings are angled that way for "lack of maintainence" reasons rather than design. When I looked at it closely there was some definite damage around the wing roots so I think they have just somewhat sagged over time.
I was thinking SU-6 at one time as well but the canopy looks wrong to me. All of the photos and the like I have seen of the SU-6 have a rear firing machine gun position and this plane does not.
I don't think it is an SU-2 either because the overall lines do not seem to match up particularly in that this plane looks "stocky" and the SU-2 looks "long an skinny" to me if that makes sense.
Thanks for the ideas though and if you think of any other possibles let me know!