A couple of former colleagues work there out of Gaydon I think. They’re happy with their lot and tried to get me on it buy after explaining the pay I decided against it. Different rates for driving, waiting, payments per vehicle which changed according to vehicle type (car, van etc) and tbh I’m too lazy to keep track of it other than hours worked and it sound like you’d need to keep track.
Only 4 on 4 off I’d do would be how it worked when I did it previously - salaried. So if you were in four days from Thursday to Sunday you’d be paid the same as a three day (pay) week where you worked Monday to Wednesday (not including the Sunday from previous pay week) so as to flatten the peaks and troughs.