Porsche 924 Clucth slipping

[Tom217]

I’m hoping on some advice on a slipping clutch under load (if I put my foot down at low rpm). I’ve tried adjusting the clutch cable by increasing the length, on a road test the clutch felt better but the bite point was basically on the floor, I’ve tried tightening the nuts making it shorter and it increases the bite height but doesn’t feel as good. I’ve also tried pulling away in both 3rd and 4th at 1500 rpm and the car stalled both times (but that’s the only check on clutch condition I’ve checked)
Any advice would be great,
Cheers