I am actually not a big fan of my southbend clutch.
I have the dual-friction one, however, I do have a problem with it slip on anything over the 100HP DP Tune in 5th and OD. Sometimes in 4th too depending on the temperature of the day.
That is not really a big problem for me, as I drive it on the stock tune most of the time. However, the extremly soft pedal (even with the spring removed) is softer than my RX7s and my other trucks. I do not like the feel at all, and it just generally feels weird - esp when my stock 80s japanese car with a 1.3L has a stiffer clutch pedal with more feel.
I plan on using an original ford pressure plate in the future when I have enough money to replace the clutch again. I regret not using the OEM stuff in the first place...