I've seen a few tools tried one before wasn't all than keen on it. What have others used? Did anyone find a wire gap tool that would fit in the hoop to check?
honestly i just got a cheap like 10 dollar set of thickness gauges from nappa and then took my dremel to the few sizes i needed, cutting out an L shape on them until they fit through the hoop.
It's been a while, however, I have a set of feelers that I got at Advanced, IIRC, they fit in the loop to measure. There are threads on the board if you search on this topic.