I've tested this 100-ways to Sunday.. and even Monday..
My results show that it might help.. a little.. maybe?.. on some radios.. I think? Basically, any improvement was so slight, i wasn't even sure if it was an improvement or just my very vivid imagination, and it certainly wasn't worth risking my reputation by looking dumb walking around with a piece of wire wagging from my radio.
It should be noted that it almost always did show an improvement in SWR on my meter - but, a slightly lower SWR does not necessarily mean more farz