I've found platform pedals work better than the tradition Campy Record style design, but the rear plate can still be uncomfortable with soft-soled shoes.

What I've found to work are Adidas "Col d'Izoard" out of production touring shoes, Adidas "Team Adidas" sneakers, and Puma "Lab II" sneakers. They all have smooth uppers and soles, and a fairly stiff sole. Not as stiff as a Diadora leather sole road shoe, but good enough. I still get significant discomfort from the rear plate from the touring shoes - maybe they are breaking down after 20 years.