I've thought of adding a power receptacle in the inboard left flap bulkhead. It would only be exposed with the flaps full down. I am very reluctant to have one forward of the wing due to the risk of whacking some poor soul with the prop. I've never had to use external power for a start, but I've come close and sure didn't want to pull the cowling (my batteries are on the firewall). I think there is enough room in that location for the standard receptacle.

Bill Kennedy
N42BK 200 hours