I'm not clear as to whether Father Terry Marks (whom I knew personally) was ever formally a member of the SSPX, or whether he was more of an "SSPX helper" along the lines of Fr Ronald Ringrose (at that time) or Fr Leo Carley. Does anybody know? He and I never discussed it. I do know that I showed up at Mass one time with a massive high-gain TV antenna in my car (it's a hobby of mine) that I'd picked up at a warehouse earlier in the day, and he found that intriguing. I liked him very much.
Requiescat in pace.