Canon IPF8300 and digital negatives

I have a new Canon IPF8300. When I try to feed OHP cut sheet material to print a digital negative, the printer cannot recognize the sheet size and just spits it out with an error message.

An email to Canon was no help as they said if the material is clear, the printer cannot "see" it to align it. I know others are printing on this material with IPF printers.

Any help would be appreciated.

Try sticking a piece of masking tape along the underside of the OHP (short edge) or try putting a sheet of paper under the OHP and feeding them through together
Davidh