I wouldn’t say uncomfortable, it feels slightly sore after use, nothing too major, just when touched really I can feel it behind the glans..
It feels as if it is getting a good stretch though, that’s the important part
That discomfort behind the glans isn’t what I’m referring to - that is where your attachment device is digging in. With an extender the stretch itself should feel just slightly uncomfortable, but tolerable for long periods of time. Perhaps this is what you mean by a good stretch?