Definitely a Sig Mid-Star. Very nice job.
Mods:
1. vortex fences, wing tip plates, whatever you want to call em
2. added flaps
3. looks like aileron servos put in wing. thou with what looks to be no access panels?
4. rudder area increased
5. maybe the elevator area increased slightly - hard to tell for sure
6. looks like the front hatch might have been changed slightly

Cheers.