I was told that the first place you'd spot ice on a PA28 was on the front of the fuel cap ridge.
Would I be correct in summising that you might expect the not so dangerous (but I wouldn't try it) rime ice collecting on those kinds of surfaces. The clear ice (the lethal stuff) would need room to runback before forming. If so could it be a false indication in the sense that no ice on the cap (or any narrow edge) doesn't mean an ice free wing?