I've tried the Pictorico Ultra Premium OHP film and it loads fine but it's definitely milky.
I'll give Magiclee a call for more info on their film. Problems I've had in the past with clear Oce film were slow drying times with pigment inks (instant dry with dye inks, apparently) and easily scratched, both of which I can't deal with on a job with ten foot long prints.
How different is the 8400 from the 8300? I've never had problems printing on Pictorico OHP on my 8300, and it's basic clear transparency film. I've never needed to resort to any tricks to get it to sense the film.