5 friction/clutch clearance issue in a 904

I'm trying to use 5 clutches/frictions in the front clutch assembly on my 904, and I'm running into a clearance issue. Before the wave snap ring goes in, a pressure plate must first go over the clutches/frictions. With the extra clutch/friction, I don't have enough clearance to install the snap ring. The pressure plate is too thick. Is there a modified pressure plate that I need? Can I just use an extra steel in place of the pressure plate? Thanks guys.