My wife and I made one of those for her dual band HT. It does extend the transmit range beyond the range of the rubber duck that came with the radio. Location makes a big difference, too. Higher is better (note the long length of the feed line in that linked antenna); away from metal and brick buildings, trees, etc.
Those antennas can overdrive the receiver - the receiver expects the crap signal the rubber duck delivers. I don't know of any damage from the stronger signal, but it can make the reception difficult to understand.
On the clip-on reel antennas, I have one from radio shack that clips onto the metal extended antenna of my radio shack receiver. I'm not sure how well that would work on the VX7 antenna, which is coated in rubber or something. Obviously, RF gets through the insulation. I'd say it's worth a try, but also try wrapping the wire antenna around the rubber duck a dozen or so times to see if that works any better. For HF reception, a long wire will work much better than the rubber duck; again, location is key. Resonance is good, but for receiving only, it's not as necessary as for transmit.