You could clip off a triangle from a corner, take about half and inch, 15mm, or so from each holder in turn. Do it in the dark (obviously) and develop in your 35mm tanks using any standard sort of developer and time, with swishing-about as agitation. If it looks as though the image-area of the film has more exposure than the rebate, then develop the sheet in your 35mm tanks (assuming you have a double reel tank or bigger) using a thin elastic band and the taco method - the big question would be which developer and timing of course. If the film-sheet corner simply appears to be evenly fogged (!) then you could try shooting with it and resort to your previous plan for developing the film, or use the taco-method again.