The clamps I have seen put the cable straight through, not looped as you did.
But they are very different. More like a block of metal with one or two holes lengthwise for the aircraft cable and at least two screws pushing onto the aircraft cable from the side.
I can imagine that your solution was not nice for your fingers...
The bass builder who changed my coathanger to an aircraft cable told me that he ordered some special built clamps for him. Probably not really needed, but I think there are better clamps than yours for this task.
There are about 140 kg load on that wire, so a good clamp is important. And letting the wire stick out a bit (seal the end with something, maybe a plastic cap plus hot glue), so you an easily adjust the tailpiece wire length.
An alternative is a carbon tailwire that can be knotted, but most people think that aircraft cable is the best solution.