A collector over on the Blowout boards states he knows a Frank Thomas collector who has completed the entire 90 card diffractor set. I really hope this is true and he's able to get some proof of it!
http://www.blowoutcards.com/forums/baseball/666490-what-some-good-90s-inserts-go-after.html
http://www.blowoutcards.com/forums/baseball/666490-what-some-good-90s-inserts-go-after.html