eluate blinds

So I've been making positive eluate blinds in order to train staff. I freeze patient plasma with known antibodies and usually spike with 1-2 drops of commercial antisera. The one antibody I cannot get to stick is the Kidds, even if I extend the incubation time, add more commercial antisera, or use a higher plasma to cells ratio. Has anyone has had any luck with getting a Kidd positive eluate made? The only other idea I had was ficin treating the cells first and then incubating with Kidd+ plasma.