Single-bushing 14.7kV pigs. Thoughts?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "J. Aaron Holmes" <jaholmes-at-silicon-arcana-dot-com> 

After months of searching and drooling over
hopelessly-expensive 5kVA units on eBay, I finally
found a cheap local source for used pigs (in Seattle).
  The price was $100 for a 14,760V 15kVA unit, the
smallest unit they had.  I was so ecstatic, I bought
two for twice the price :)  Never hurts to have a
spare, after all.

Trouble is, they're the single-bushing sort.

Now, this may or may not be a big deal; I've been a
long-time lurker on this list, but I've never gotten a
good feeling for exactly what the downside is to
having only a single HV bushing.  If I wire up the
outer two bushings on the LV side and ground the case,
can't I just treat the case like the other HV bushing?

Sounds like most people with single-bushing units have
the 7200V variety, so series-phasing them makes sense
for several reasons.  I'm not sure what good it does
me, though.

If this has been dealt with a million times, feel free
to scorch me.  I deserve it :)

Regards,
Aaron