So far there's one confirmed date that Jimi played with Jimmy Soul, the Lovers (aka the Squires) with Jimi on guitar backed him up on this date: 

Friday 25 February 1966
"Winter Weekend", Alumni Gym, Union College, Schenectady, New York
Complete line-up: Jack Ely And The Kingsmen, Jimmy Soul

This was the second day of a two day "Winter Festival" weekend during which Jimi played guitar behind Jimmy Soul and the Ronettes and bass with the Drifters - see Jimi Hendrix at Union College 1966