I'll let you try it and report back, but I wouldn't do it. People have been making beer without SF6 for ten thousand years. At the least it's an unnecessary expense. Unless you have a very great deal of headspace the offgasing of dissolved CO2 when you rack your beer will protect it. Additionally, if you're racking to 2ndary in order to actually have a 2ndary fermentation, such as with fruit, you'll be generating a surplus of protective CO2. Similarly, unless you're reckless when bottling there should be a minimum of O2 in the bottle if bottle conditioning and virtually none if bottling from a carbed keg. You can use oxygen barrier caps as well. Lastly, without prior knowledge, I'd be wary of deliberately introducing sulfur anything to an acidic environment like beer.