I finally found a use for my tiny film holders. The Instax Mini film fits well enough to make exceptional images (not blurry , light struck junk). Caveats: 1) The Fidelity Deluxe 2 1/4 x 3 1/4 film holders need to have the flap at the bottom trimmed. Needs to be trimmed just enough to clear the processing bubble, yet still allow the dark slide to engage and hold the flap closed. The scrap of the first one I cut (by eye) measured 8.5mm when I checked. When cutting the flap on the other side I left even more of the flap so it would engage better, and that scrap measured 7.6mm. 2) It is a little challenging getting the exposed film back in the Instax cassette. My trick is to push out an un-exposed film just a few millimeters, to open the trap. Once the trap is open, slide the exposed filim OVER the unexposed one and push them both back in. The issue is the flap, as it closes, catches the junction of the image area and paper on the viewing side of the film as you try to push it back in the cassette. Maybe the safety flap can just be removed from the cassette. Otherwise it works perfect! So well, that my 'Instax Graflok Back' conversion is on hold.