Thanks Benz. The reason for my question is that I got conflicting information from Spinlock UK on another of their clutches, and I usually try and get feedback from actual users, who sometimes have a different view than the marketing
The other reason is that in testing several brands of clutches, Practical Sailor found the Constrictor textile clutch held small diameter line very well, but larger size ( 12mm from memory) slipped.
But having said all that, I would be very pleased if they did perform well. They are MUCH kinder on covers than ceramic or even anodised alloy jaws and plates.
Maybe someone who has used the XTX will see this thread, and comment....