987 Coffin Arm Ball joint

[563]

I am replacing the coffin arms on the rear of our 2006 Cayman S and am unable to split the ball joint. I have tried the 2 hammer technique and a tuning fork wedge. I have a joint splitter with the pivot in the middle and a large bolt at the end but this does not go sufficiently into the joint to put pressure squarely on the ball joint nut. I have been spraying with Wurthe Rust Off and have tried a little heat from a small plumbing torch but I am reluctant to overheat the alloy upright. Would be grateful for any useful suggestions.