However, after trying several different brands of transparency material, I have found that Fixxons Waterproof Inkjet Screen Positive Film works as good at the Pictorico film.
Since the Fixxons film cost $33 for a pack of 100 (8.5" x 11") while
Pictorico film cost $22 for a pack of 20 (therefore $110 per 100) ,
I was compelled to switch to Fixxons.
These scanned prints are side-by-side comparisons of the two transparency films in my own workflow for KM73 photopolymer plates. For each image, the step wedge on the top is Pictorico and the step wedge on the bottom is Fixxons.
The final prints were scanned with an Epson Perfection V500, with all color controls/profiles turned off. I made my new curves with the top print. You can see that, for each of the large rectangles (11 step wedge), I used the blur-->average filter in photoshop to get an easy/accurate reading. The photo on the bottom is the same plate, with slightly less pressure on the etching press.
What is most encouraging is that 50% density is about the same with both films, and close enough to 50% in reality to be left alone in the adjustment curve (a nice feature in any process).
The next logical experiment is to shoot a plate with the adjustment(compensation) curves applied and see if the step wedge can be made closer to the digital version.