Might could have done it.

source: 
LAGS
Entry: 
447
Example: 
Might could have done it.
Modal 1: 
might
Modal 2: 
could
Gender: 
Male
Race/Ethnicity: 
White
Age: 
77
Level of Education: 
High school and business college
Home Community, Town, or State: 
MS (Macon)
Location Collected: 
MS (Macon)
Year: 
1974
Relation to Addressee: 
subject to fieldworker
Medium: 
Spoken
Sentence Structure: 
1.0
Status: 
Naturalistic