I saw them in Flint, in the '70's, at the old IMA auditorium. They opened for Yes, who couldn't fill the venue themselves. My friends and I were all big Yes fans. Through a connection, we were paid $10 each to man an aisle between the audience and the stage, our job being to keep the people off the tables that were serving as a barrier. Basically, a promoter saving money on security. Worked for us, but the union put a stop to it before the next show.
I'd never heard of J. Geil's, but enjoyed the show. They've always seemed to me very competent but not particularly original or distinctive. Time for ghost/tribute bands!