Hi Riri
I use silhouettes but haven't had that much cannula showing. Obviously with the silhouette you see more cannula than with the quickset, but usually only 1-2mm. The only way to be sure if you weren't pumping saline would be to keep a close eye on your sugars and change the set if it didn't seem to be working well (assuming you'd eliminated other possible causes).
I've had some where my sugars haven't seemed as stable, and when I've removed the set it's been bruised (under the plastic connector where I couldn't see it). Today for the first time the cannula came out kinked, which may explain a big rise in my bs overnight.
Hope this helps - though after just 3 months I'm not exactly an expert on sets myself!