Might should have.

source: 
LAGS
Entry: 
545
Example: 
Might should have.
Modal 1: 
might
Modal 2: 
should
Gender: 
Male
Race/Ethnicity: 
White
Age: 
76
Level of Education: 
6th grade
Home Community, Town, or State: 
GA (Decatur County)
Location Collected: 
GA (Calvary)
Year: 
1970
Relation to Addressee: 
subject to fieldworker
Medium: 
Spoken
Sentence Structure: 
1.0
Status: 
Naturalistic