Ah the penny drops. When I fitted mine I just pulled back the wheel trying to get the tension right and then fiddling to do up the axle nuts trying to keep everything square
I have them on my TSR2 but I thought they were specific to belt drives/and or could only be used in horizontal dropouts that are open at the rear. Looking at the different types I can see that they can also be used for forward facing dropouts, in that they are offset. I need to get myself a pair.
Its great you learn something new every day
Regards
Jerry