You will need to expose Type 55 one to one and a half stops more than
looks right on the print in order to have adequate detail in the
negative. Increasing development time and temperature will result in
some contrast rise, but it will still be a soft negative by alt.process
standards. Palladio paper with a hefty dose of peroxide added to the
developer is reputed to do well by type 55's, and Ziatype with strong
ammonium dichromate contrasting agent in the mix should do very well
indeed. I wouldn't expect anything but very soft results from regular
Pt/Pd.---Carl