In the past I have used PMK with 8x10 Tri-X film to do my platinum printing. I find that the pyro stain facilitates in the creation of the platinum image. Once I inadvertantly put the vinyl border masking material on the base side of the negative and after an extended exposure I noticed lines on my negative where the masking material was in place. Has anyone else who may be reading this post had this experience? Lately I've taken to shooting with the Toyo CF 4x5 (about 1/3 lighter in weight than my 8x10) and then making enlarged negatives with APHS film (as described by Bob Herbst on his web site). This way I will be protecting my precious original negatives from damaging UV light. I would be very interested in anyone's thoughts on this.